Exchange coupling film and magnetoresistive element using the same

ABSTRACT

A PtMn alloy film known as an antiferromagnetic material having excellent corrosion resistance is used for an antiferromagnetic layer. However, an exchange coupling magnetic field is decreased depending upon the conditions of crystal grain boundaries. Therefore, in the present invention, the crystal grain boundaries formed in an antiferromagnetic layer (PtMn alloy film) and the crystal grain boundaries formed in a ferromagnetic layer are made discontinuous in at least a portion of the interface between both layers. As a result, the antiferromagnetic layer can be appropriately transformed to an ordered lattice by heat treatment to obtain a larger exchange coupling magnetic field than a conventional element.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an exchange coupling film comprising anantiferromagnetic film and a ferromagnetic film so that themagnetization direction of the ferromagnetic layer is pinned in apredetermined direction by an exchange coupling magnetic field producedbetween the antiferromagnetic layer and the ferromagnetic layer.Particularly, the present invention relates to an exchange coupling filmwhich produces a large exchange coupling magnetic field, and amagnetoresistive element (a spin valve thin film element or an AMRelement) using the exchange coupling magnetic field, and a thin filmmagnetic head using the magnetoresistive element.

2. Description of the Related Art

A spin valve thin film element is a GMR (giant magnetoresistive) elementutilizing a giant magnetoresistive effect, for detecting a recordingmagnetic field from a recording medium such as a hard disk or the like.

The spin valve thin film element has some advantages that the structureis relatively simple as compared with other GMR elements, and theresistance changes with a weak magnetic field.

The simplest structure of the spin valve thin film element comprises anantiferromagnetic layer, a pinned magnetic layer, a nonmagneticintermediate layer and a free magnetic layer.

The antiferromagnetic layer and the pinned magnetic layer are formed incontact with each other so that the pinned magnetic layer is put into asingle domain state and the magnetization direction thereof is pinned ina predetermined direction by an exchange coupling magnetic fieldproduced at the interface between the antiferromagnetic layer and thepinned magnetic layer.

Magnetization of the free magnetic layer is oriented in the directioncrossing the magnetization direction of the pinned magnetic layer bybias layers formed on both sides of the free magnetic layer.

The antiferromagnetic layer generally comprises a Fe—Mn (iron-manganese)alloy film, a Ni—Mn (nickel-manganese) alloy film, or a Pt—Mn(platinum-manganese) alloy film. Particularly, the Pt—Mn alloy film hasvarious advantages of the high blocking temperature, excellent corrosionresistance, etc., and thus gets into the spotlight.

The inventors found that even with an antiferromagnetic layer comprisinga PtMn alloy film, an exchange coupling magnetic field produced betweenthe antiferromagnetic layer and a pinned magnetic layer cannot beincreased depending upon conditions.

With the antiferromagnetic layer comprising a PtMn alloy film, theantiferromagnetic layer is transformed from a disordered lattice to anordered lattice by heat treatment after the antiferromagnetic layer andthe pinned magnetic layer are laminated, thereby producing an exchangecoupling magnetic field.

However, it was found that when the interface between theantiferromagnetic layer and the ferromagnetic layer is put into acoherent state in which the atoms of the constituent antiferromagneticmaterial of the antiferromagnetic layer have one-to-one correspondencewith the atoms of the constituent soft magnetic material of the pinnedmagnetic layer, the antiferromagnetic layer is not appropriatelytransformed to the ordered lattice, thereby failing to produce a largeexchange coupling magnetic field.

SUMMARY OF THE INVENTION

The present invention has been achieved for solving the above problem,and an object of the present invention is to provide an exchangecoupling film which can produce a large exchange coupling magnetic fieldwhen an antiferromagnetic material containing element X (a platinumgroup element) and Mn is used as an antiferromagnetic layer, amagnetoresistive element using the exchange coupling film, and a thinfilm head using the magnetoresistive element.

In order to achieve the object of the present invention, there isprovided an exchange coupling film comprising an antiferromagnetic layerand a ferromagnetic layer, which are formed in contact with each otherso that the magnetization direction of the ferromagnetic layer is pinnedin a predetermined direction by an exchange coupling magnetic fieldproduced at the interface between the antiferromagnetic layer and theferromagnetic layer, wherein the antiferromagnetic layer is made of anantiferromagnetic material comprising element X (at least one elementselected from Pt, Pd, Ir, Rh, Ru, and Os) and Mn, and in a section ofthe exchange coupling film in parallel with the thickness directionthereof, the crystal grain boundaries formed in the antiferromagneticlayer and the crystal grain boundaries formed in the ferromagnetic layerare discontinuous in at least a portion of the interface.

In the present invention, the crystal grain boundaries mean boundarieswhere two crystal grains contact each other while maintaining differentcrystal orientations, and include boundaries (so-called twin boundaries)where the atomic arrangements of two crystal grains have mirrorsymmetry. In “Physics of Metal Material” (Nikkan Kogyo Shinbun (issuedon Feb. 28, 1992)), p58, a twin boundary is described as an example of“special boundaries”, and it is defined that crystal grain boundariesinclude twin boundaries.

In the present invention, with respect to the crystal orientations ofthe antiferromagnetic layer and the ferromagnetic layer, differentcrystal planes may be preferentially oriented in parallel with the filmplane, but the same equivalent crystal planes are preferablypreferentially oriented.

More specifically, in the antiferromagnetic layer and the ferromagneticlayer according to the present invention, equivalent crystal planesrepresented by a {111} plane are preferentially oriented in parallelwith the interface. The {111} plane is a general term for equivalentcrystal planes in a single crystal structure and is represented by usingMiller indices. The equivalent crystal planes include a (111) plane, a(-111) plane, a (1-11) plane, a (11-1) plane, (-1-11) plane, a (1-1-1)plane, a (-11-1) plane, and a (-1-1-1) plane.

In another aspect of the present invention, an exchange couplingmagnetic film comprises an antiferromagnetic layer and a ferromagneticlayer, which are formed in contact with each other so that themagnetization direction of the ferromagnetic layer is pinned in apredetermined direction by an exchange coupling magnetic field producedat the interface between the antiferromagnetic layer and theferromagnetic layer, wherein in the antiferromagnetic layer, anequivalent crystal plane represented by a {111} plane is preferentiallyoriented in parallel with the interface, and a twin crystal is formed inat least a portion of the antiferromagnetic layer so that the twinboundaries of the twin crystal are formed in nonparallel with theinterface.

In the present invention, in the antiferromagnetic layer, the equivalentcrystal plane represented by the {111} plane is preferentially orientedin parallel with the interface. In order to orient the {111} plane ofthe antiferromagnetic layer, it is effective to form a seed layer belowthe antiferromagnetic layer.

In the present invention, the inner angle between each of the twinboundaries and the interface is preferably 68° to 76°. With the innerangle in this range, the {111} plane of the antiferromagnetic layer ispreferentially oriented in parallel with the interface.

Furthermore, in the present invention, the equivalent crystal planerepresented by the {111} plane of the ferromagnetic layer is preferablypreferentially oriented in parallel with the interface.

As in the present invention, in cases in which the equivalent crystalplanes represented by the {111} plane of both the antiferromagneticlayer and the ferromagnetic layer are preferentially oriented inparallel with the interface, a high rate of change in resistance can beobtained.

In the present invention, the antiferromagnetic layer is preferably madeof an antiferromagnetic material comprising element X (at least oneelement selected from Pt, Pd, Ir, Rh, Ru, and Os) and Mn.

In the present invention, a seed layer is formed below theantiferromagnetic layer so that the equivalent crystal planesrepresented by the {111} plane of the antiferromagnetic layer and theferromagnetic layer are oriented in parallel with the film plane, asdescribed above.

The exchange coupling film of the present invention preferably comprisesthe antiferromagnetic layer and the ferromagnetic layer which arelaminated in this order from the bottom, and the seed layer formed belowthe ferromagnetic layer and having a crystal structure mainly comprisinga face-centered cubic crystal in which an equivalent crystal planerepresented by the {111} plane is preferentially oriented in parallelwith the interface.

In the present invention, the seed layer is provided below theantiferromagnetic layer, as describe above, so that the equivalentcrystal planes represented by the {111} plane of the antiferromagneticlayer and the ferromagnetic layer are preferentially oriented inparallel with the film plane.

In the present invention, the seed layer is preferably made of a NiFealloy, Ni, a Ni—Fe—Y alloy (wherein Y is at least one element selectedfrom Cr, Rh, Ta, Hf, Nb, Zr, and Ti), or a Ni—Y alloy.

The seed layer is represented by the composition formula(Ni_(1-x)Fe_(x))_(1-y)Y_(y) (x and y are atomic ratios) wherein atomicratio x is preferably 0 to 0.3, and atomic ratio y is preferably 0 to0.5. The seed layer is preferably nonmagnetic at room temperature.

In the present invention, an underlying layer comprising at least oneelement selected from Ta, Hf, Nb, Zr, Ti, Mo and W is preferably formedbelow the seed layer.

Furthermore, in the present invention, at least a portion of theinterface between the antiferromagnetic layer and the seed layer ispreferably in an incoherent state. The incoherent state means that theconstituent atoms of the antiferromagnetic layer do not have one-to-onecorrespondence with the constituent atoms of the ferromagnetic layer(the seed layer nonmagnetic at room temperature) at the interfacetherebetween. On the other hand, the coherent state means that the atomshave one-to-one correspondence at the interface.

In the present invention, the crystal grain boundaries formed in theantiferromagnetic layer and the crystal grain boundaries formed in theferromagnetic layer are discontinuous in at least a portion of theinterface, as described above. However, this crystal structure ispreferably also formed in the interface between the antiferromagneticlayer and the seed layer.

Namely, in the present invention, the crystal grain boundaries formed inthe antiferromagnetic layer and the crystal grain boundaries formed inthe seed layer are discontinuous in at least a portion of the interface.As a result, the antiferromagnetic layer is appropriately transformed tothe ordered lattice without being restrained by the crystal structure ofthe seed layer during heat treatment, whereby a large exchange couplingmagnetic field can be obtained.

In the present invention, the antiferromagnetic layer may be made of aX—Mn—X′ alloy (wherein X′ represents at least one element selected fromNe, Ar, Kr, Xe, Be, B, C, N, Mg, Al, Si, P, Ti, V, Cr, Fe, Co, Ni, Cu,Zn, Ga, Ge, Zr, Nb, Mo, Ag, Cd, Ir, Sn, Hf, Ta, W, Re, Au, Pb, and therare earth elements). In this case, the X—Mn—X′ alloy is an interstitialsolid solution in which element X′ enters the interstices between spacelattices composed of the element X and Mn, or a substitution solidsolution in which the lattice points of crystal lattices composed of theelement X and Mn are partially substituted by the element X′. This canincrease the lattice constant of the antiferromagnetic layer to permitthe formation of an atomic arrangement in which atoms do not haveone-to-one correspondence with the atoms of the ferromagnetic layer atthe interface with the ferromagnetic layer.

In the present invention, the composition ratio of the element X orelements (X+X′) is preferably 45 at % to 60 at %. The experimentalresults described below indicate that with a composition ratio of theelement X or elements (X+X′) in the above range, an exchange couplingmagnetic field of at least 1.58×10⁴ (A/m) can be obtained. Thecomposition ratio of the element X or elements (X+X′) is more preferably49 at % to 56.5 at %.

In the present invention, at least a portion of the interface betweenthe antiferromagnetic layer and the ferromagnetic layer is preferablyincoherent.

In the present invention, the above-described exchange coupling film canbe applied to various magnetoresistive elements.

A magnetoresistive element of the present invention comprises anantiferromagnetic layer, a pinned magnetic layer formed in contact withthe antiferromagnetic layer so that the magnetization direction ispinned by an exchange coupling magnetic field with the antiferromagneticlayer, a free magnetic layer formed on the pinned magnetic layer with anonmagnetic intermediate layer provided therebetween, and a bias layerfor orienting the magnetization direction of the free magnetic layer ina direction crossing the magnetization direction of the pinned magneticlayer, wherein the antiferromagnetic layer and the pinned magnetic layerformed in contact with the antiferromagnetic layer comprise theabove-described exchange coupling film.

A magnetoresistive element of the present invention may comprise anantiferromagnetic layer, a pinned magnetic layer formed in contact withthe antiferromagnetic layer so that the magnetization direction ispinned by an exchange coupling magnetic field with the antiferromagneticlayer, a free magnetic layer formed on the pinned magnetic layer with anonmagnetic intermediate layer provided therebetween, andantiferromagnetic exchange bias layers formed on or below the freemagnetic layer with a space corresponding to a track width Tw, whereinthe exchange bias layers and the free magnetic layer comprise theabove-described exchange coupling film, and magnetization of the freemagnetic layer is pinned in a predetermined direction.

A magnetoresistive element of the present invention may comprisenonmagnetic layers laminated on and below a free magnetic layer, pinnedmagnetic layers located on one of the nonmagnetic intermediate layersand below the other nonmagnetic intermediate layer, antiferromagneticlayers located on one of the pinned magnetic layers and below the otherpinned magnetic layer, for pinning the magnetization direction of eachof the pinned magnetic layers in a predetermined direction by anexchange coupling magnetic field, and a bias layer for orienting themagnetization direction of the free magnetic layer in a directioncrossing the magnetization direction of the pinned magnetic layers,wherein the antiferromagnetic layers and the pinned magnetic layersrespectively formed in contact with the antiferromagnetic layerscomprise the above-described exchange coupling film.

An magnetoresistive element of the present invention may comprise amagnetoresistive layer and a soft magnetic layer which are laminatedwith a nonmagnetic layer provided therebetween, and antiferromagneticlayers formed on or below the magnetoresistive layer with a spacetherebetween corresponding to a track width Tw, wherein theantiferromagnetic layers and the magnetoresistive layer comprise theabove-described exchange coupling film.

A thin film head of the present invention comprises the above-describedmagnetoresistive element, and shield layers formed on and below themagnetoresistive element with gap layers provided therebetween.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of the structure of a single spin valvemagnetoresistive element in accordance with a first embodiment of thepresent invention, as viewed from the ABS side;

FIG. 2 is a sectional view of the structure of a single spin valvemagnetoresistive element in accordance with a second embodiment of thepresent invention, as viewed from the ABS side;

FIG. 3 is a sectional view of the structure of a single spin valvemagnetoresistive element in accordance with a third embodiment of thepresent invention, as viewed from the ABS side;

FIG. 4 is a sectional view of the structure of a single spin valvemagnetoresistive element in accordance with a fourth embodiment of thepresent invention, as viewed from the ABS side;

FIG. 5 is a sectional view of the structure of a dual spin valvemagnetoresistive element in accordance with a fifth embodiment of thepresent invention, as viewed from the ABS side;

FIG. 6 is a sectional view of the structure of an AMR magnetoresistiveelement in accordance with a sixth embodiment of the present invention,as viewed from the ABS side;

FIG. 7 is a sectional view of the structure of an AMR magnetoresistiveelement in accordance with a seventh embodiment of the presentinvention, as viewed from the ABS side;

FIG. 8 is a schematic drawing showing the deposition state of themagnetoresistive element shown in FIG. 1;

FIG. 9 is a schematic drawing showing the structure of the laminatedfilm shown in FIG. 8 after heat treatment;

FIG. 10 is a schematic drawing showing the deposition state of themagnetoresistive element shown in FIG. 5;

FIG. 11 is a schematic drawing showing the structure of the laminatedfilm shown in FIG. 10 after heat treatment;

FIG. 12 is a partial sectional view showing the structure of a thin filmhead (reproducing head) of the present invention;

FIG. 13 is a graph showing the relation between the Pt amount andexchange coupling magnetic field (Hex) of an antiferromagnetic layer(PtMn alloy film) obtained by changing the Pt amount;

FIG. 14 is a drawing schematically showing the crystal orientations ofan antiferromagnetic layer and a ferromagnetic layer of an exchangecoupling film of the present invention;

FIG. 15 is a drawing showing the crystal orientations of anantiferromagnetic layer and a ferromagnetic layer of an exchangecoupling film of a comparative example;

FIG. 16 is a transmission electron beam diffraction image of a spinvalve film of the present invention from the direction parallel to thefilm plane;

FIG. 17 is a transmission electron beam diffraction image of a spinvalve film of a comparative example from the direction parallel to thefilm plane;

FIG. 18 is a partial schematic drawing of the transmission electron beamdiffraction image shown in FIG. 16;

FIG. 19 is a partial schematic drawing of the transmission electron beamdiffraction image shown in FIG. 17;

FIG. 20 is a schematic drawing of a transmission electron beamdiffraction image of an antiferromagnetic layer of the present inventionfrom the direction perpendicular to the film plane;

FIG. 21 is a schematic drawing of a transmission electron beamdiffraction image of a ferromagnetic layer of the present invention fromthe direction perpendicular to the film plane;

FIG. 22 is a schematic drawing of the state in which the transmissionelectron beam diffraction images shown in FIGS. 20 and 21 aresuperposed;

FIG. 23 is a schematic drawing of a transmission electron beamdiffraction image of an antiferromagnetic layer of a comparative examplefrom the direction perpendicular to the film plane;

FIG. 24 is a schematic drawing of a transmission electron beamdiffraction image of a ferromagnetic layer of a comparative example fromthe direction perpendicular to the film plane;

FIG. 25 is a schematic drawing of the state in which the transmissionelectron beam diffraction images shown in FIGS. 23 and 24 aresuperposed;

FIG. 26 is a transmission electron microscope photograph of a section ofa spin valve thin film element of the present invention, taken along adirection parallel to the thickness direction;

FIG. 27 is a transmission electron microscope photograph of a section ofa spin valve thin film element of a comparative example, taken along adirection parallel to the thickness direction;

FIG. 28 is a partial schematic drawing of the transmission electronmicroscope photograph of FIG. 26;

FIG. 29 is a partial schematic drawing of the transmission electronmicroscope photograph of FIG. 27;

FIG. 30 is a transmission electron microscope photograph of a section ofa spin valve thin film element of another example of the presentinvention, taken along a direction parallel to the thickness direction;and

FIG. 31 is a partial schematic drawing of the transmission electronmicroscope photograph of FIG. 30

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a sectional view of a single spin valve magnetoresistiveelement according to a first embodiment of the present invention, asviewed from the ABS side. FIG. 1 shows only the central portion of theelement in the X direction.

The single spin valve magnetoresistive element is provided at thetrailing side end of a flying slider provided on a hard disk device, fordetecting a recording magnetic field from a hard disk or the like. Themovement direction of the magnetic recording medium such as the harddisk or the like coincides with the Z direction, and the direction of aleakage magnetic field from the magnetic recording medium coincides withthe Y direction.

In FIG. 1, an underlying layer 6 made of a nonmagnetic material composedof at least one element selected from Ta, Hf, Nb, Zr, Ti, Mo and W isformed at the bottom. The underlying layer 6 is provided forpreferentially orienting, in parallel with the film plane, an equivalentcrystal plane represented by a {111} plane of a seed layer 22 formed onthe underlying layer 6. The underlying layer 6 is formed to a thicknessof, for example, about 50 Å.

The seed layer 22 is mainly composed of a face-centered cubic crystal inwhich an equivalent crystal plane represented by the {111} plane ispreferentially oriented in parallel with the interface with anantiferromagnetic layer 4. The seed layer 22 is preferably made of aNiFe alloy, Ni, a Ni—Fe—Y alloy (wherein Y is at least one elementselected from Cr, Rh, Ta, Hf, Nb, Zr and Ti), or a Ni—Y alloy.

The seed layer 22 is preferably represented by the composition formula(Ni_(1-x)Fe_(x))_(1-y)Y_(y) (x and y are atomic ratios) wherein theatomic ratio x is preferably 0 to 0.3, and the atomic ratio y ispreferably 0 to 0.5. This can increase the degree of preferentialorientation of the {111} plane in each of the antiferromagnetic layer 4and layers formed thereon, thereby increasing the rate AR/R of change inresistance.

The term “equivalent crystal planes” represents crystal lattice planesindicated by Miller indices, and the equivalent crystal planesrepresented by the {111} plane include a (111) plane, a (-111) plane, a(1-11) plane, a (11-1) plane, a (-1-11) plane, a (1-1-1) plane, a(-11-1) plane and a (-1-1-1) plane.

Namely, in the seed layer 22 of the present invention, the (111) plane,or the (1-11) plane or the like equivalent thereto is preferentiallyoriented in parallel with the film plane.

In the present invention, the seed layer 22 is preferably nonmagnetic atroom temperature. With the seed layer 22 nonmagnetic at roomtemperature, deterioration in asymmetry of a waveform can be prevented,and the resistivity of the seed layer 22 can be increased by the effectof the element Y (described below) added for making the layernonmagnetic, thereby suppressing a shunt of a sensing current flowingfrom a conductive layer to the seed layer 22. When the sensing currentis easily shunted to the seed layer 22, a decrease in the rate (ΔR/R) ofchange in resistance and Barkhausen noise undesirably occur.

In order to make the seed layer 22 nonmagnetic, a Ni—Fe—Y alloy or Ni—Yalloy (wherein Y is at least one element selected from Cr, Rh, Ta, Hf,Nb, Zr and Ti) can be selected from the above materials. These materialspreferably have a face-centered cubic crystal structure in which anequivalent crystal plane represented by the {111} plane ispreferentially oriented in parallel with the film plane. The seed layer22 is formed to a thickness of, for example, about 30 A.

The antiferromagnetic layer 4 is formed on the seed layer 22. Theantiferromagnetic layer 4 is preferably made of an antiferromagneticmaterial comprising element X (at least one element selected from Pt,Pd, Ir, Rh, Ru, and Os) and Mn.

A X—Mn alloy comprising such a platinum group element is an excellentantiferromagnetic material having the excellent properties that it hasexcellent corrosion resistance and a high blocking temperature, and theexchange coupling magnetic field (Hex) can be increased. Particularly,Pt among the platinum group elements is preferred. For example, abinary-system PtMn alloy can be used.

In the present invention, the antiferromagnetic layer 4 may be made ofan antiferromagnetic material comprising the element X, element X′ (X′is at least one element selected from Ne, Ar, Kr, Xe, Be, B, C, N, Mg,Al, Si, P, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, Cd,Ir, Sn, Hf, Ta, W, Re, Au, Pb, and the rare earth elements), and Mn.

Preferably, a type of element capable of entering into interstices inthe lattice formed by X and Mn and making an interstitial solid solutionor a type of element capable of displacing some of the lattice points inthe crystal lattice formed by X and Mn and making a substitutional solidsolution is used as the element X′. Herein, “solid solution” refers to asolid in which components thereof are homogeneously mixed within asingle crystal phase.

In an interstitial solid solution or substitution solid solution, thelattice constant of the X—Mn—X′ alloy can be increased, as compared withthe lattice constant of the X—Mn alloy film. Therefore, the differencefrom the lattice constant of the pinned magnetic layer 3 which will bedescribed below can be increased, thereby easily bringing theinterfacial structure between the antiferromagnetic layer and the pinnedmagnetic layer 3 into an incoherent state. Particularly, in use of theelement X′ which dissolves in the substitution solid solution, with anexcessively high composition ratio of element X′, the antiferromagneticproperties deteriorate to decrease the exchange coupling magnetic fieldproduced at the interface with the pinned magnetic layer 3.Particularly, in the present invention, a rare gas element (at least oneof Ne, Ar, Kr and Xe) of inert gas is preferably used as the element X′in the interstitial solid solution. Such a rare gas element is an inertgas element, and thus has less effect on the antiferromagneticproperties even when the rare gas element is contained in the film.Furthermore, Ar or the like is a gas conventionally introduced as asputtering gas into a sputtering apparatus, and can easily be entered inthe film only by appropriately controlling the gas pressure.

When a gaseous element is used as the element X′, it is difficult tocontain a large amount of element X′ in the film. However, in use of arare gas, the exchange coupling magnetic field produced by heattreatment can be significantly increased by entering only a small amountof gas in the film.

In the present invention, the composition ratio of the element X′ ispreferably in the range of 0.2 at % to 10 at %, and more preferably inthe range of 0.5 at % to 5 at %. Furthermore, the element X ispreferably Pt, and thus a Pt—Mn—X′ alloy is preferably used.

The pinned magnetic layer 3 comprising a three-layer film is formed onthe antiferromagnetic layer 4.

The pinned magnetic layer 3 comprises a Co film 11, a Ru film 12 and aCo film 13, in which the magnetization directions of the Co films 11 and13 are put into an antiparallel state by an exchange coupling magneticfield at the interface with the antiferromagnetic layer 4 and RKKYantiferromagnetic coupling between the Co films 11 and 13 through the Rufilm 12. This is referred to as a “ferrimagnetic coupling state”. Thisconstruction can stabilize magnetization of the pinned magnetic layer 3,and increase the exchange coupling magnetic field produced at theinterface between the pinned magnetic layer 3 and the antiferromagneticlayer 4.

For example, the Co film 11 is formed to a thickness about 20 Å, the Rufilm 12 is formed to a thickness of about 8 Å, and the Co film 13 isformed to a thickness of about 15 Å.

The pinned magnetic layer 3 may comprise a three-layer film or a singlelayer film. Each of the films 11, 12 and 13 may be made of a materialother that the above magnetic materials. For example, each of the layers11 and 13 may be made of CoFe other than Co.

A nonmagnetic intermediate layer 2 is formed on the pinned magneticlayer 3. The nonmagnetic intermediate layer 2 is made of, for example,Cu. When the magnetoresistive element of the present invention is atunnel magnetoresistive element (TMR element) using a tunnel effect, thenonmagnetic intermediate layer 2 is made of an insulating material, forexample, Al₂O₃ or the like.

Furthermore, a free magnetic layer 1 comprising a two-layer film isformed on the nonmagnetic intermediate layer 2.

The free magnetic layer 1 comprises two films including a NiFe alloyfilm 9 and a Co film 10. As shown in FIG. 1, the Co film 10 is formed onthe side in contact with the nonmagnetic intermediate layer 2 to preventdiffusion of metal elements at the interface with the nonmagneticintermediate layer 2, thereby increasing AR/R (the rate of change inresistance).

The NiFe alloy film 9 is composed of, for example, 80 at % of Ni and 20at % of Fe. For example, the thickness of the NiFe alloy film 9 is about45 Å, and the thickness of the Co film 10 is about 5 Å.

As shown in FIG. 1, a protecting film 7 made of a nonmagnetic materialcomprising at least one element selected from Ta, Hf, Nb, Zr, Ti, Mo andW is formed on the free magnetic layer 1.

Furthermore, hard bias layers 5 and conductive layers 8 are formed onboth sides of a laminate ranging from the underlying film 6 to theprotecting film 7. The magnetization of the free magnetic layer 1 isoriented in the track width direction (the X direction shown in thedrawing) by a bias magnetic field from the hard bias layers 5.

The hard bias layers 5 are made of, for example, a Co—Pt(cobalt-platinum) alloy, a Co—Cr—Pt (cobalt-chromium-platinum) alloy, orthe like, and the conductive films 8 are made of α-Ta, Au, Cr, Cu(copper), W (tungsten), or the like. In the tunnel magnetoresistiveelement, the conductive layers 8 are respectively formed below the freemagnetic layer 1 and above the antiferromagnetic layer 4.

In the present invention, a backed layer made of a metal material or anonmagnetic metal such as Cu, Au, or Ag may be formed on the freemagnetic layer 1. For example, the backed layer is formed to a thicknessof about 12 to 20 Å.

The protecting layer 7 is preferably made of Ta or the like, andcomprises an oxide surface layer.

By forming the backed layer, the mean free path of +spin (up spin)electrons which contribute to the magnetoresistive effect is extended toobtain a high rate of change in resistance by a so-called spin filtereffect in a spin valve magnetic element, whereby the magnetic elementcan cope with a higher recording density.

In the present invention, heat treatment is performed after each of thelayers is deposited to produce an exchange coupling magnetic field (Hex)at the interface between the antiferromagnetic layer 4 and the pinnedmagnetic layer 3 so that the magnetization direction of the pinnedmagnetic layer 3 is pinned in the height direction (the Y directionshown in the drawing). However, after heat treatment, the spin valvethin film element has the following crystal orientation.

The crystal orientation will be described on the basis of the exchangecoupling film mainly comprising the antiferromagnetic layer and theferromagnetic layer (pinned magnetic layer).

As described above, in the present invention, the seed layer 22 isformed below the antiferromagnetic layer 4. The seed layer 22 is formedso that the equivalent crystal plane represented by the {111} plane ispreferentially oriented in parallel with the film plane, and thus theantiferromagnetic layer is also formed on the seed layer 22 so that thesame crystal plane as the seed layer 22 is preferentially oriented inparallel with the film plane.

For example, when the (-111) plane of the seed layer 11 ispreferentially oriented in parallel with the film plane, the (-111)plane of the antiferromagnetic layer 4 formed on the seed layer 22 isalso preferentially oriented in parallel with the film plane.

In the pinned magnetic layer 3 formed on the antiferromagnetic layer 4,the same equivalent crystal plane as the antiferromagnetic layer 4 ispreferentially oriented in parallel with the film plane.

Namely, in the present invention, in the seed layer 22, theantiferromagnetic layer 4 and the pinned magnetic layer 3, the sameequivalent crystal planes represented by the {111} plane arepreferentially oriented in parallel with the film plane.

In the present invention, the crystal planes preferentially oriented inparallel with the film plane are preferably the equivalent crystalplanes represented by the {111} plane because the crystal planes areclosest-packed planes. For example, when the environmental temperatureor the sensing current density in a magnetic head device is increased,particularly thermal stability is required. However, where theequivalent crystal planes represented by the {111} plane, which are theclosest-packed planes, are preferentially oriented, atomic diffusion inthe thickness direction less occurs to increase the thermal stability atthe interface between layers of the film, thereby improving thestability of characteristics.

In the present invention, in the antiferromagnetic layer 4 and thepinned magnetic layer 3, the same equivalent crystal planes arepreferentially oriented in parallel with the film plane, and at leastsome of the same crystal axes present in the crystal planes are orientedin different directions in the antiferromagnetic layer 4 and the pinnedmagnetic layer 3.

Such crystal orientation possibly depends upon the conditions fordepositing the antiferromagnetic layer 4 and the pinned magnetic layer 3in the deposition step (before heat treatment).

For example, when the material and the composition ratio of theantiferromagnetic layer 4 and the deposition conditions thereof arecontrolled so that the lattice constant of the antiferromagnetic layer 4is sufficiently larger than the lattice constant of the pinned magneticlayer 3, the antiferromagnetic layer 4 and the pinned magnetic layer 3are possibly less epitaxially grown.

In epitaxial deposition, the antiferromagnetic layer 4 and the pinnedmagnetic layer 3 are easily deposited so that all crystal orientationsin the antiferromagnetic layer 4 have parallel relation to those in thepinned magnetic layer 3. Therefore, the same equivalent crystal planesare preferentially oriented in parallel with the interface between theantiferromagnetic layer 4 and the pinned magnetic layer 3, and the sameequivalent crystal axes present in the crystal plane of theantiferromagnetic layer 4 and the pinned magnetic layer 3 are orientedin the same direction, thereby easily causing one-to-one correspondencebetween the atomic arrangements of the antiferromagnetic layer 4 and thepinned magnetic layer 3 at the interface between both layers (refer toFIG. 15). FIG. 15 shows an example in which [110] orientations presentin the (111) planes of an antiferromagnetic layer 31 and a ferromagneticlayer 30 are in the same direction.

When such crystal orientation occurs in the step before heat treatment,the antiferromagnetic layer 4 is restrained by the crystal structure ofthe pinned magnetic layer 3 even by performing the heat treatment tofail to cause appropriate ordering transformation, significantlydecreasing the exchange coupling magnetic field.

In the present invention, the antiferromagnetic layer 4 and the pinnedmagnetic layer 3 are possibly deposited without being epitaxially grown,and in this deposition state, heat treatment is performed to causeappropriate ordering transformation of the antiferromagnetic layer 4without being restrained by the crystal structure of the pinned magneticlayer 3. In observation of the film structure of the spin valve film ofthe present invention after the heat treatment, the same equivalentcrystal planes of the antiferromagnetic layer 4 and the pinned magneticlayer 3 are preferentially oriented in parallel with the film plane,while other crystal planes of the antiferromagnetic layer 4 and thepinned magnetic layer 3, which are not oriented in parallel with thefilm planes, have no parallel relation. As a result, at least some ofthe same equivalent crystal axes present in the crystal planes orientedin parallel with the film plane are oriented in different directions inthe antiferromagnetic layer 4 and the pinned magnetic layer 3.

In the present invention, as one method for producing theabove-described crystal orientation, the seed layer 22 is provided belowthe antiferromagnetic layer 4. As described above, in theantiferromagnetic layer 4 and the pinned magnetic layer 3 formed on theseed layer 22, the same equivalent crystal planes are preferentiallyoriented in parallel with the film plane by providing the seed layer 22,and this crystal orientation causes a high rate of change in resistance(ΔR/R).

In the present invention, at least some of the same equivalent crystalaxes present in the crystal planes oriented in parallel with the filmplane are oriented in different directions in the antiferromagneticlayer 4 and the pinned magnetic layer 3. Such crystal orientation ispossibly due to the fact that the antiferromagnetic layer 4 isappropriately transformed from the face-centered cubic lattice as adisordered phase to a CuAu-I type face-centered tetragonal lattice as anordered phase without being restrained by the crystal structure of theferromagnetic layer 3. Therefore, a large exchange coupling magneticfield can be obtained, as compared with a conventional element. In thepresent invention, at least a portion of the crystal structure of theantiferromagnetic layer 4 may be transformed to the CuAuI typeface-centered tetragonal ordered lattice by heat treatment.

In the present invention, in order to obtain a large exchange couplingmagnetic field, it is important to have the following crystal structure.

Namely, in the above-described section of the spin valve film of thepresent invention, the crystal grain boundaries observed in theantiferromagnetic layer 4 and the crystal gain boundaries observed inthe pinned magnetic layer 3 are discontinuous in at least a portion ofthe interface between both layers.

The crystal grain boundaries represent boundaries where two crystalgrains contact each other while maintaining different crystalorientations, and include boundaries (so-called twin boundaries) wherethe atomic arrangements of two crystal grains have mirror symmetry. Thegrain boundaries (1), (2), (3) and (5) shown in FIG. 28 are the formerboundaries having no special symmetric relation, and the grainboundaries (4), (8), (9), (10) and (11) shown in FIG. 28 are likely tobe the latter twin boundaries.

As shown in FIG. 26 and 28 (FIG. 26 is a transmission electronmicroscope photograph (TEM photograph), and FIG. 28 is a schematicdrawing of the photograph of FIG. 26), the crystal grain boundaries (4),(5), (8), (9), (10), and (11) formed in the PtMn alloy film (theantiferromagnetic layer 4) and the crystal grain boundaries (1), (2) and(3) formed in the layer formed on the antiferromagnetic layer 4 arediscontinuous at the interface between both layers. In thisdiscontinuous state, it can be supposed that at least some of the sameequivalent crystal axes present in the crystal plane of theantiferromagnetic layer 4 and the crystal plane of the pinned magneticlayer 3 in the direction of the film plane are oriented in differentdirections. The other example shown in FIGS. 30 and 31 indicates thatthe grain boundaries without the special symmetric relation and the twinboundaries formed in the antiferromagnetic layer, and the grainboundaries formed in the ferromagnetic layer are also discontinuous atthe interface between both layers.

FIG. 26 is a transmission electron microscope (TEM) photograph of asection of a spin valve film according to the present invention, takenalong the direction parallel to the thickness direction, and FIG. 28 isa schematic drawing thereof.

The spin valve film shown in FIG. 26 has the structure, from the bottom,Si substrate/Al₂O₃/under layer: Ta (3 nm)/seed layer:Ni₈₀Fe₂₀/antiferromagnetic layer: Pt₅₄Mn₄₆ (15 nm)/pinned magneticlayer: Co (1.5 nm)/Ru (0.8 nm)/Co (2.5 nm)/nonmagnetic intermediatelayer: Cu (2.5 nm)/free magnetic layer: Co (1 nm)/Ni₈₀Fe₂₀ (3 nm)/backedlayer: Cu (1.5 nm)/Ta/Ta oxide film. The numerical value in parenthesesof each of the layers represents the thickness. The composition ratiosof the seed layer, the antiferromagnetic layer and the free magneticlayer are shown by at %.

The antiferromagnetic layer and the pinned magnetic layer were depositedby a DC magnetron sputtering apparatus at an Ar gas pressure of 3 mTorr.In deposition of the antiferromagnetic layer, the distance between thesubstrate and a target was 80 nm.

The spin valve film having the above structure was heat-treated afterdeposition. The heat treatment was performed at a temperature of, forexample, 200° C. or more, for 2 hours or more with a degree of vacuum of10⁻⁷ Torr.

The transmission electron microscope photograph of FIG. 26 shows thestate after the heat treatment.

FIG. 26 indicates that no interface is observed between the adjacentlayers formed on PtMn (antiferromagnetic layer), and thus a state like asingle layer is observed. This is possibly due to the fact that thelayers formed on the PtMn alloy film are composed of elements having theatomic numbers close to each other, and have uniform crystalorientation, and thus the layers have similar properties of electronbeam absorption and diffraction, causing little difference in contrastbetween the layers in a transmission electron microscope image.

However, as shown in FIG. 26, the interface between the PtMn alloy filmand the layers formed on the PtMn alloy film is clearly observed.

Furthermore, the crystal grain boundaries formed in the PtMn alloy filmand the crystal grain boundaries appearing in the layers formed on thePtMn alloy film are clearly observed. The crystal grain boundaries aremostly formed to extend in the thickness direction.

Referring to the schematic drawing of FIG. 28 showing the spin valvefilm of the present invention, for example, the crystal grain boundary(5) formed in the PtMn alloy film and the crystal grain boundaries (1),(2) and (3) formed in each of the layers formed on the PtMn alloy filmare found to be discontinuous at the interface between the PtMn alloyfilm and the layers formed thereon.

The crystal grain boundaries (1), (2), (3) and (5) are considered asboundaries where two crystal grains contact each other while maintainingdifferent crystal orientations. On the other hand, crystal grainboundaries (4), (8), (9), (10) and (11) are considered as twinboundaries where atomic arrangements have mirror-symmetry in a singlecrystal grain. The twin boundaries easily occur in parallel with eachother.

It is also found that the crystal grain boundaries (4), (8), (9), (10)and (11) are discontinuous at the interface with the crystal grainboundaries (1), (2) and (3) formed in the layers above the PtMn alloyfilm.

The cause why the crystal grain boundaries formed in theantiferromagnetic layer and the crystal grain boundaries formed in theferromagnetic layer are discontinuous at the interface between bothlayers will be described below. However, in the spin valve thin filmelement shown in FIG. 26 which is a transmission electron microscopephotograph, the exchange coupling magnetic field is significantlyincreased, resulting in the achievement of an exchange coupling magneticfield of about 10.9×10⁴ (A/m).

In the present invention, at least some of the twin grain boundaries ofthe twin crystal are formed in nonparallel with the interface. This isshown in FIGS. 26 and 28.

Namely, as shown in FIGS. 26 and 28, a twin crystal is formed in theantiferromagnetic layer, and the grain boundaries (4), (8), (9), (10)and (11), which are twin boundaries, occur in the twin crystal. All ofthe twin boundaries are nonparallel to the interface.

FIG. 30 is a transmission electron microscope (TEM) photograph of asection of a film having a different film structure from that shown inFIG. 26, taken along a direction parallel to the thickness direction.

This film has the structure, from the bottom, Si substrate/Al₂O₃/underlayer: Ta (3 nm)/seed layer: Ni₈₀Fe₂₀ (2 nm)/antiferromagnetic layer:Pt₄₉Mn₅₁ (16 nm)/pinned magnetic layer: Co₉₀Fe₁₀ (1.4 nm)/Ru (0.9nm)/Co₉₀Fe₁₀ (2.2 nm)/nonmagnetic intermediate layer: Cu (2.2 nm)/freemagnetic layer: Co₉₀Fe₁₀ (1 nm)/Ni₈₀Fe₂₀ (4 nm)/Ta (3 nm). The numericalvalue in parentheses of each of the layers represents the thickness. Thecomposition ratios of the seed layer, the antiferromagnetic layer andthe free magnetic layer are shown by at %.

The antiferromagnetic layer and the pinned magnetic layer were depositedby a DC magnetron sputtering apparatus at an Ar gas pressure of 2.5mTorr. In deposition of the antiferromagnetic layer, the distancebetween the substrate and a target was 80 nm.

The spin valve film having the above structure was heat-treated afterdeposition. The heat treatment was performed at a temperature of, forexample, 270° C. or more, for 4 hours with a degree of vacuum of 10⁻⁷Torr. In this example, the composition ratio, the thickness and thedeposition conditions of the PtMn were different from those shown inFIG. 26.

The transmission electron microscope photograph of FIG. 30 shows thestate after the heat treatment. An electron beam diffraction image ofthis film indicates that in the antiferromagnetic layer and theferromagnetic layer, the {111} plane is preferentially oriented inparallel with the interface.

FIG. 31 is a schematic drawing of the TEM photograph of FIG. 30. FIG. 31indicates that a plurality of twin boundaries are formed in theantiferromagnetic layer, and all the twin boundaries are nonparallel tothe interface with the ferromagnetic layer.

In a case in which a twin crystal is formed in an antiferromagneticlayer, and twin boundaries are formed in the twin crystal in nonparallelwith the interface, as in the present invention, the antiferromagneticlayer is appropriately transformed from a disordered lattice to anordered lattice by heat treatment, resulting in a large exchangecoupling magnetic field. With the film structure shown in FIG. 30, theexchange coupling magnetic field is about 9.3×10⁴ (A/m).

Whether or not the twin boundaries are formed in the deposition step isnot important. Even when the twin boundaries are not formed in thedeposition step, the twin boundaries according to the present inventionare possibly produced by heat treatment.

In the present invention, the atoms of the antiferromagnetic layer areunlikely to be constrained by the crystal structure of the ferromagneticlayer. In this way, with weak force of restraint at the interface, theantiferromagnetic layer is easily transformed from the disorderedlattice to the ordered lattice. However, lattice strain occurs duringthe transformation, and thus the transformation cannot be effectivelycaused unless the lattice strain is appropriately relieved. In thetransformation, possibly, the atoms of the antiferromagnetic layer arerearranged from the disordered lattice to the ordered lattice to producelattice strain, and at the same time, the atomic arrangement is changedto mirror symmetry at short distance intervals to relieve the latticestrain. After heat treatment, the boundaries of change to mirrorsymmetry become twin boundaries. The formation of such twin boundariesmeans that ordering transformation occurs during the heat treatment.

In this case, the twin boundaries are formed in the direction crossingthe interface between the antiferromagnetic layer and the ferromagneticlayer near the interface to relieve the lattice strain produced inrearrangement of the atoms in parallel with the interface. Therefore,when appropriate ordering transformation occurs over the entire layer,the twin boundaries are formed in nonparallel with the interface. Thisis true for the present invention. When the twin boundaries are formedin nonparallel with the interface, as in the present invention, a largeexchange coupling magnetic field can be obtained. On the other hand,when the atoms cannot be rearranged in parallel with the interface,i.e., when the atoms of the antiferromagnetic layer are stronglyconstrained by the crystal structure of the ferromagnetic layer at theinterface between both layers, the twin boundaries are not formed acrossthe interface. In this case, the twin boundaries are not formed, or thetwin boundaries are formed in parallel with the interface.

Where a plurality of twin boundaries are formed in the same twincrystal, as shown in FIGS. 26 and 30, the twin boundaries aresubstantially parallel to each other.

In the example shown in FIG. 30, the grain boundaries formed in theantiferromagnetic layer have no special symmetric relation with thegrain boundaries formed in the ferromagnetic layer, and the grainboundaries and the twin boundaries formed in the antiferromagnetic layerand the grain boundaries formed in the ferromagnetic layer are found tobe discontinuous at the interface between both layers.

It is thus found that the crystal structures shown in FIGS. 26, 28, 30and 31 are apparently different from the crystal structure shown inFIGS. 27 and 29 (FIG. 27 is a transmission electron microscopephotograph (TEM photograph), and FIG. 29 is a schematic drawing of thephotograph of FIG. 27). In FIGS. 27 and 29, the crystal grain boundariesformed in the PtMn alloy film (the antiferromagnetic layer 4) and thecrystal grain boundaries formed in the layer formed on the PtMn alloyfilm are continuous at the interface between both layers, and a largecrystal grain is formed to extend across the interface between theantiferromagnetic layer 4 and the layer formed thereon.

FIG. 27 is a transmission electron microscope (TEM) photograph of asection of a conventional spin valve film taken along the directionparallel to the thickness direction, and FIG. 29 is a schematic drawingthereof.

The conventional spin valve film has the structure, from the bottom, Sisubstrate/Al₂O₃/under layer: Ta (3 nm)/seed layer: Ni₈₀Fe₂₀ (2nm)/antiferromagnetic layer: Pt₄₄Mn₅₆ (13 nm)/pinned magnetic layer: Co(1.5 nm)/Ru (0.8 nm)/Co (2.5 nm)/nonmagnetic intermediate layer: Cu (2.5nm)/free magnetic layer: Co (1 nm)/Ni₈₀Fe₂₀ (3 nm)/backed layer: Cu (1.5nm)/Ta/Ta oxide film. The numerical value in parentheses of each of thelayers represents the thickness. The composition ratios of the seedlayer, the antiferromagnetic layer and the free magnetic layer are shownby at %.

This film structure is different from the structure of the spin valvefilm of the present invention in the Pt amount and thickness of the PtMnalloy film (antiferromagnetic layer), and deposition conditions.

The antiferromagnetic layer and the pinned magnetic layer were depositedby a DC magnetron sputtering apparatus at an Ar gas pressure of 0.8mTorr. In deposition of the antiferromagnetic layer, the distancebetween the substrate and a target was 50 nm.

The spin valve film having the above structure was heat-treated afterdeposition. The heat treatment was performed at a temperature of, forexample, 200° C. or more, for 2 hours or more with a degree of vacuum of10⁻⁷ Torr.

The transmission electron microscope photograph of FIG. 27 shows thestate after the heat treatment.

FIG. 27 indicates that a crystal grain block occurs to extend across theinterface between the PtMn alloy film and the layers formed thereon inthe thickness direction.

Referring to the schematic drawing of FIG. 29, crystal grain boundaries(6) and (7) are formed to extend across the interface between the PtMnalloy film and the layers formed on the PtMn alloy film. Namely, in thespin valve film as a comparative example, the crystal grain boundariesformed in the PtMn alloy film and the crystal grain boundaries formed inthe layers above the PtMn alloy film are continuous at the interface.

The crystal grain boundaries (6) and (7) are considered as crystal grainboundaries where two crystal grains contact each other while maintainingdifferent crystal orientations, and no twin boundary is possibly formedin the antiferromagnetic layer.

In the spin valve thin film element shown in the transmission electronmicroscope photograph of FIG. 27, the exchange coupling magnetic fieldis very small, and thus only an exchange coupling magnetic field ofabout 0.24×10⁴ (A/m) can be obtained.

As described above, the present invention is different from aconventional example in the positions of the crystal grain boundariesformed in the antiferromagnetic layer and the crystal grain boundariesformed in the ferromagnetic layer at the interface between both layers.

In order to make the crystal grain boundaries formed in theantiferromagnetic layer and the crystal grain boundaries formed in theferromagnetic layer discontinuous at the interface between both layers,as in the present invention, the composition of the antiferromagneticlayer is important, and the deposition conditions are also important.The deposition conditions include the heat treatment temperature, theheat treatment time, and the Ar gas pressure, the distance between thesubstrate and the target, the substrate temperature, the substrate biasvoltage, the deposition rate, etc. during deposition of theantiferromagnetic layer and the ferromagnetic layer.

On the other hand, like in the comparative example shown in FIG. 29, inthe antiferromagnetic layer having a different composition and depositedunder different deposition conditions from the present invention, thecrystal grain boundaries formed in the antiferromagnetic layer and thecrystal grain boundaries formed in the ferromagnetic layer are easily ina continuous state at the interface between both layers.

In the present invention in which the crystal grain boundaries arediscontinuous at the interface, possibly, the antiferromagnetic layerand the ferromagnetic layer are not epitaxially grown in the depositionstep, and thus the constituent atoms of the antiferromagnetic layer arenot strongly restricted by the crystal structure of the ferromagneticlayer. Therefore, the antiferromagnetic layer is appropriatelytransformed from a disordered lattice to an ordered lattice in heattreatment, resulting in a large exchange coupling magnetic field.

On the other hand, in the comparative example in which the crystalgrains are continuos at the interface, possibly, the antiferromagneticlayer and the ferromagnetic layer are epitaxially grown in thedeposition step, and thus the constituent atoms of the antiferromagneticlayer are strongly restricted by the crystal structure of theferromagnetic layer. Therefore, the antiferromagnetic layer cannot beproperly transformed from a disordered lattice to an ordered lattice inheat treatment, resulting in a small exchange coupling magnetic field.

In both the spin valve thin film elements respectively shown in thetransmission electron microscope photographs of FIG. 26 and 27, latticefringes of the {111} plane are observed in parallel with the film plane.It is thus recognized that in the antiferromagnetic layer and theferromagnetic layer of each of the present invention and the comparativeexample, the crystal planes equivalent to the {111} plane arepreferentially oriented in parallel with the film plane.

When the same equivalent crystal planes are preferentially oriented inthe antiferromagnetic layer and the ferromagnetic layers, as describedabove, a high rate (ΔR/R) of change in resistance can be obtained.

In the exchange coupling film having the crystal grain boundaries shownin FIGS. 26, 28, 30 and 31, as in the present invention, theantiferromagnetic layer 4 and the pinned magnetic layer 3 are possiblydeposited without being epitaxially grown in the deposition step tocause appropriate ordering transformation of the antiferromagnetic layer4 by heat treatment without being restrained by the crystal structure ofthe pinned magnetic layer 3. Therefore, a large exchange couplingmagnetic field can be obtained.

It is also found that the grain boundaries (4), (8), (9), (10) and (11)shown in FIG. 28, i.e., the twin boundaries, are nonparallel to theinterface. It is also found that the twin boundaries in the otherexample shown in FIGS. 30 and 31 are nonparallel to the interface. Inthe antiferromagnetic layer in any of the examples of the presentinvention, the equivalent crystal planes represented by the {111} planeare preferentially oriented in parallel with the interface due to theseed layer provided below the antiferromagnetic layer.

A twin crystal represents a solid material in which at least two singlecrystals combine with each other according to specified symmetricrelation. The twin boundary is formed in the twin crystal so that atomicarrangements are mirror symmetric with respect to the twin boundary as aboundary. Such a twin crystal is produced to relieve internal stress.Even when the twin boundary is formed to promote relief of internalstress, the occurrence of great internal stress in a portion makes itimpossible to appropriately relieve the internal stress at the twinboundary. Therefore, grain boundaries like the grain boundary (5) shownin FIG. 28 and the grain boundaries shown in FIG. 30 are formed, inwhich two crystal grains contact each other while maintaining differentcrystal orientations. As a result, the great internal stress is possiblyrelieved.

When the twin boundaries formed in the antiferromagnetic layer arenonparallel to the interface according to the present invention, atleast some of the same equivalent crystal axes present in the crystalplanes of the antiferromagnetic layer and the pinned magnetic layer 3 inthe direction of the film plane are oriented in different directions atthe interface between both layers.

The large exchange coupling magnetic field cannot be obtained unless theantiferromagnetic layer 4 is transformed from the disordered lattice tothe ordered lattice by heat treatment. However, during transformation,the atomic arrangement is changed to mirror symmetry to form the twinboundaries, relieving lattice strain produced in movement of atoms inthe direction parallel to the interface and in the thickness direction.At this time, the twin boundaries are formed in nonparallel with theinterface.

In appropriate transformation of the antiferromagnetic layer from thedisordered lattice to the ordered lattice, the twin boundariesnonparallel to the interface are formed in the antiferromagnetic layerto produce the large exchange coupling magnetic field. In this case, aplurality of twin boundaries may be formed in a twin crystal so that thetwin boundaries are substantially parallel to each other.

On the other hand, in the comparative example shown in FIGS. 27 and 29,no twin boundary is formed in the antiferromagnetic layer. This isbecause the atoms in the antiferromagnetic layer are not rearranged bytransformation during heat treatment. Therefore, transformation from thedisordered lattice to the ordered lattice less proceeds, and only asmall exchange coupling magnetic field can be obtained.

Even when the twin boundaries are formed in the antiferromagnetic layer,with the twin boundaries parallel to the interface, lattice strain inthe thickness direction is supposed to be relieved to some extent.However, the atoms are not rearranged in parallel with the interface,and thus the antiferromagnetic layer is not appropriately transformedfrom the disordered lattice to the ordered lattice at the interface.Therefore, the exchange coupling magnetic field is decreased.

In the present invention, the inner angle θ (refer to FIGS. 28 and 31)between each of the twin boundaries and the interface is preferably 68°to 76°. The inner angle θ shown in FIG. 28 is about 68°, and the innerangle θ shown in FIG. 31 is about 75°. With the inner angle in thisrange, the equivalent crystal plane represented by the {111} plane ofthe antiferromagnetic layer is preferentially oriented in parallel withthe interface. In the pinned magnetic layer 3, preferably, theequivalent crystal plane represented by the {111} plane ispreferentially oriented in parallel with the interface. This permitseffective improvement in the rate of change in resistance.

In the present invention, when the diffraction pattern described belowis observed in a transmission electron beam diffraction image of thecrystal orientation of each of the antiferromagnetic layer 4 and thepinned magnetic layer 3 after deposition and heat treatment, the crystalorientations of the antiferromagnetic layer 4 and the pinned magneticlayer 3 can be supposed to be as follows. The same equivalent crystalplanes are preferentially oriented in parallel with the interfacebetween the antiferromagnetic layer 4 and the pinned magnetic layer 3,and at least some of the crystal axes present in the crystal planes areoriented in different directions in the antiferromagnetic layer 4 andthe pinned magnetic layer 3.

In the present invention, an electron beam is incident from thedirection parallel to the interface between the antiferromagnetic layer4 and the pinned magnetic layer 3 to obtain a transmission electron beamdiffraction image of each of the antiferromagnetic layer 4 and thepinned magnetic layer 3.

In the transmission electron beam diffraction image of each of theantiferromagnetic layer 4 and the pinned magnetic layer 3, a diffractionspot corresponding to a reciprocal lattice point corresponding to eachof the crystal planes appear. The reciprocal lattice point (=diffractionspot) represents a crystal plane by Miller indices, for example, such asthe (110) plane.

The diffraction spot is indexed. Since the distance r between the originand the diffraction spot is inversely proportional to the latticespacing d, the spacing d can be determined by measuring the distance r.The spacing of each crystal plane {hkl} of PTMn, CoFe, NiFe or the likeis known to some extent, and thus each diffraction spot can be indexedby {hkl}. A general document of transmission electron beam diffractionimages shows a transmission electron beam diffraction pattern of each ofsingle crystal structures in which each diffraction spot is indexed byspecified {hkl} observed or calculated in each of directions of acrystal grain. The document is used to determine which diffraction spotof a crystal plane in a single crystal structure is the same as orsimilar to each of the diffraction spots obtained in the transmissionelectron beam diffraction image of each of the antiferromagnetic layer 4and the pinned magnetic layer 3. The same {hkl} indexing as the singlecrystal is performed for each of the diffraction spots.

The transmission electron beam diffraction image of theantiferromagnetic layer 4 is superposed on the transmission electronbeam diffraction image of the pinned magnetic layer 3 so that the beamorigins are caused to coincide with each other.

Alternatively, a transmission electron beam diffraction image isobtained in a range in which an electron beam is simultaneously appliedto both the antiferromagnetic layer 4 and the pinned magnetic layer 3.

In the present invention, a first virtual line connecting the beamorigin and a diffraction spot indicating a crystal plane and located inthe thickness direction as viewed from the beam origin in thediffraction image of the antiferromagnetic layer 4 coincides with afirst virtual line connecting the beam origin and a diffraction spothaving the same indices as the antiferromagnetic layer 4 in thediffraction image of the pinned magnetic layer 3 (refer to FIGS. 16 and18; FIG. 16 is a transmission electron beam diffraction image, and FIG.18 is a schematic drawing of the diffraction image of FIG. 16). Thismeans that in the antiferromagnetic layer 4 and the pinned magneticlayer 3, the same equivalent crystal planes are preferentially orientedin the direction of the film plane.

In the present invention, a second virtual line connecting the beamorigin and a diffraction spot indicating a crystal plane and located ina direction other than the thickness direction as viewed from the beamorigin in the diffraction image of the antiferromagnetic layer 4deviates from a second virtual line connecting the beam origin and adiffraction spot having the same indices as the antiferromagnetic layerin the diffraction image of the pinned magnetic layer 3 (refer to FIGS.16 and 18). This means that the crystal planes of the antiferromagneticlayer 4 and the pinned magnetic layer 3, which are not oriented inparallel with the film plane, are not parallel to each other.Alternatively, when a diffraction spot indicating a crystal plane andlocated in a direction other than the thickness direction as viewed fromthe beam origin is observed only in the diffraction image of one of theantiferromagnetic layer 4 and the ferromagnetic layer, the crystalplanes of the antiferromagnetic layer 4 and the pinned magnetic layer 3,which are not oriented in parallel with the film plane, are not parallelto each other.

In the present invention, it is possible to obtain a diffraction imageapparently different from that of the comparative example shown in FIGS.17 and 19 (FIG. 17 is a transmission electron beam diffraction image,and FIG. 19 is a schematic drawing of the diffraction image of FIG. 17).In the comparative example shown in FIGS. 17 and 19, the second virtualline connecting the beam origin and a diffraction spot indicating acrystal plane and located in a direction other than the thicknessdirection as viewed from the beam origin in the diffraction image of theantiferromagnetic layer 4 coincides with the second virtual lineconnecting the beam origin and a diffraction spot having the sameindices as the antiferromagnetic layer in the diffraction image of thepinned magnetic layer 3.

When such a transmission electron beam diffraction image as shown inFIG. 16 is obtained, the same equivalent crystal planes of theantiferromagnetic layer 4 and the pinned magnetic layer 3 arepreferentially oriented in parallel with the film plane, and at leastsome of the same equivalent crystal axes present in the crystal planesare oriented in different directions in the antiferromagnetic layer 4and the pinned magnetic layer 3.

Each of FIGS. 16 and 17 shows a transmission electron beam diffractionimage of a section of a laminated film (spin valve film) taken along thethickness direction thereof, the image being obtained by applying anelectron beam vertically to the section (the direction parallel to thefilm plane). The transmission electron beam diffraction image shown inFIG. 16 was obtained with an electron beam aperture which permitssimultaneous irradiation of both the antiferromagnetic layer and anotherlayer with the electron beam.

FIGS. 18 and 19 are schematic drawings of the transmission electron beamdiffraction mages shown in FIGS. 16 and FIG. 17, respectively.

FIG. 16 shows the transmission electron beam diffraction image obtainedby measuring a spin valve film of the present invention having thefollowing film structure:

Al₂O₃ (3 nm)/Ta (3 nm)/seed layer: Ni₈₀Fe₂₀ (2 nm)/antiferromagneticlayer: Pt₅₄Mn₄₆ (15 nm)/pinned magnetic layer: [Co (1.5 nm)/Ru (0.8nm)/Co (2.5 nm)]/nonmagnetic intermediate layer: Cu (2.5 nm)/freemagnetic layer: [Co (1 nm)/Ni₈₀Fe₂₀ (3 nm)]/backed layer: Cu (1.5nm)/protecting layer: Ta (1.5 nm)/Ta oxide film.

FIG. 17 shows the transmission electron beam diffraction image obtainedby measuring a spin valve film of a comparative example having thefollowing film structure:

Al₂O₃ (3 nm)/Ta (3 nm)/seed layer: Ni₈₀Fe₂₀ (2 nm)/antiferromagneticlayer: Pt₄₄Mn₅₆ (13 nm)/pinned magnetic layer: [Co (1.5 nm)/Ru (0.8mn)/Co (2.5 nm)]/nonmagnetic intermediate layer: Cu (2.5 nm)/freemagnetic layer: [Co (1 nm)/Ni₈₀Fe₂₀ (3 nm)]/backed layer: Cu (1.5nm)/protecting layer: Ta (1.5 nm)/Ta oxide film Referring to FIG. 16,the diffraction spot indicating the {111} plane of PtMn and thediffraction spot indicating the {111} plane of fcc-Co/Cu/CiFe arelocated on the same line extending in the layer thickness direction.When these diffraction spots are specifically labeled, for example,(1–11) planes, the diffraction spots (-111) indicative of the crystalplane which is not parallel to the layer surface but forms 70.5 degreesangle with the (1-11) plane, are not on the same line extending from thecenter of the diffraction diagram. In other words, the crystal planesnot parallel to the layer surface do not enter a parallel relationshipbetween the PtMn layer and the pinned magnetic layer (ferromagneticlayer).

Referring to FIG. 17, the diffraction points indicative of {111} planesof PtMn and fcc-Co/Cu/NiFe (fcc-Co pinned magnetic layer is included)are on the same line extending in the layer thickness direction.Moreover, the diffraction points indicative of {200} planes are on thesame line extending from the center of the diagram. The same can beobserved for the diffraction spots other than the above-describeddiffraction spots. The diffraction diagrams of the PtMn and thefcc-Co/Cu/NiFe have every direction analogous. The reason that thediffraction diagram of PtMn is smaller than that of the fcc-Co/Cu/NiFeis that the lattice constant of PtMn is larger than that of thefcc-Co/Cu/NiFe by approximately 10 percent. PtMn and fcc-Co/Cu/NiFeexhibit perfect lattice matching, i.e., an epitaxial relationship.

In the above film structures, the numerical value in parentheses in eachof the layers represents the thickness. In the electron beam diffractionimage shown in FIG. 16, numeral “1” with “-” (bar) placed above it inthe notation of a crystal plane with Miller indices means “−1” (minus 1)and is thus described as “−1” in the specification.

In the transmission electron beam diffraction image of an example shownin FIG. 16, a diffraction spot of the antiferromagnetic layer (PtMn),which is indexed as (1-11), appears in the thickness direction.Similarly, a diffraction spot of a layer (denoted by fcc-Co/Cu/NiFe inthe electron beam diffraction image) other than the antiferromagneticlayer (PtMn), which is indexed as (1-11), appears in the thicknessdirection.

The schematic drawing of FIG. 18 showing these diffraction spotsindicates that a first virtual line connecting the beam origin and thediffraction spot indexed as (1-11) in the diffraction image of theantiferromagnetic layer coincides with a first virtual line connectingthe beam origin and the diffraction spot indexed as (1-11) in thediffraction image of a layer other than the antiferromagnetic layer.

In the transmission electron beam diffraction image of the example shownin FIG. 16, a diffraction spot of the antiferromagnetic layer (PtMn),which is indexed as (-111), also appears in a direction other than thethickness direction. Similarly, a diffraction spot of a layer (denotedby fcc-Co/Cu/NiFe in the electron beam diffraction image) other than theantiferromagnetic layer (PtMn), which is indexed as (-111), also appearsin the thickness direction.

However, as shown in FIG. 18, a second virtual line connecting the beamorigin and the above diffraction spot of PtMn indexed as (-111) deviatesfrom that of fcc-Co/Cu/NiFe.

Namely, the electron beam diffraction image of the example reveals thatthe same equivalent crystal planes represented by {111} planes of theantiferromagnetic layer and the ferromagnetic layer are preferentiallyoriented in parallel with the thickness direction, while the crystalplanes of the antiferromagnetic layer and the ferromagnetic layer, otherthan the crystal planes oriented in parallel with the film plane, arenot parallel to each other.

In the example shown in FIGS. 16 and 18, the diffraction spots (-111) ofboth the antiferromagnetic layer and the ferromagnetic layer, i.e., thediffraction spots present in a direction other than the thicknessdirection, appear in the diffraction image, but either of both layerspossibly shows no diffraction spot (-111) in the diffraction image. Inthis case, crystal planes of the antiferromagnetic layer and theferromagnetic layer, other than the crystal planes oriented in parallelwith the film plane, are not parallel to each other.

On the other hand, in the transmission electron beam diffraction imageof the comparative example shown in FIG. 17, a diffraction spot of the{111} plane of the antiferromagnetic layer (PtMn) appears in thethickness direction. Similarly, a diffraction spot of the {111} plane ofa layer (denoted by fcc-Co/Cu/NiFe in the electron beam diffractionimage) other than the antiferromagnetic layer (PtMn) appears in thethickness direction.

The diffraction spots observed in the transmission electron beamdiffraction image shown in FIG. 17 are denoted by the {111} planeincluding all equivalent crystal planes, not by the equivalent crystalplanes such as (111) plane, (11-1) plane, etc. This is because unlike inFIG. 16, other {111} diffraction spots (for example, (-111)) present indirections other than the thickness direction need not be describedhere.

In the transmission electron beam diffraction image of the comparativeexample shown in FIG. 17, a diffraction spot of the {200} plane of theantiferromagnetic layer (PtMn) appears in a direction other thethickness direction. Similarly, a diffraction spot of the {200} plane ofa layer (denoted by fcc-Co/Cu/NiFe in the electron beam diffractionimage) other than the antiferromagnetic layer (PtMn) appears in adirection other than the thickness direction.

Referring to the schematic drawing of FIG. 19, in the transmissionelectron beam diffraction image of the comparative example, thediffraction spots of the {111} planes of the antiferromagnetic layer andthe ferromagnetic layer appear in the thickness direction as viewed fromthe beam origin, and the first virtual lines connecting the beam originand the respective diffraction spots {111} of both layers coincide witheach other. Also, the second virtual lines connecting the beam originand the respective diffraction spots {200} of the antiferromagneticlayer and the ferromagnetic layer appearing in the direction other thanthe thickness direction as viewed from the beam origin coincide witheach other.

Namely, in the comparative example, crystal planes of theantiferromagnetic layer and the ferromagnetic layer in a direction otherthan the film plane direction are parallel to each other. This ispossibly due to that the antiferromagnetic layer and the ferromagneticlayer are epitaxially grown, thereby easily causing a so-called coherentstate in which the atomic arrangements of the antiferromagnetic layerand the ferromagnetic layer have one-to-one correspondence at theinterface between both layers. In the coherent state, the ferromagneticlayer cannot be appropriately transformed to the ordered lattice by heattreatment, and thus a large exchange coupling magnetic field cannot beexhibited.

As a result of measurement of an exchange coupling magnetic field (Hex)of a spin valve film having the film structure of the comparativeexample, an exchange coupling magnetic filed of as low as about 0.24×10⁴(A/m) could be obtained.

On the other hand, in the present invention, the same equivalent crystalplanes of the antiferromagnetic layer and the ferromagnetic layer arepreferentially oriented in parallel with the interface between bothlayers, but the other crystal planes of both layers are not parallel toeach other. This means that the crystal orientations of theantiferromagnetic layer and the ferromagnetic layer have rotationalrelation with respect to an axis vertical to the interface, and that atleast some of the same equivalent crystal axes present in the crystalplanes preferentially oriented in parallel with the interface areoriented in different directions in the antiferromagnetic layer and theferromagnetic layer.

It is thus thought that the atomic arrangements of the antiferromagneticlayer and the ferromagnetic layer do not have one-to-one correspondenceat the interface between both layers, and the antiferromagnetic layer isappropriately transformed to the ordered lattice without beingrestrained by the crystal structure of the ferromagnetic layer duringheat treatment of the antiferromagnetic layer. Therefore, a largerexchange coupling magnetic field can be obtained, as compared with aconventional spin valve film.

As a result of actual measurement of an exchange coupling magnetic field(Hex) of the spin valve film used in the above-described experiment inthe present invention, an exchange coupling magnetic filed of as largeas about 10.9×10⁴ (A/m) could be obtained.

With the spin valve film showing the above-described transmissionelectron beam diffraction image, appropriate ordering transformation ofthe antiferromagnetic layer 4 occurs in the heat treatment step toobtain a large exchange coupling magnetic field.

In the present invention, the diffraction spots located in the thicknessdirection preferably show the equivalent crystal planes represented bythe {111} plane.

In the present invention, when the diffraction pattern described belowis obtained in a transmission electron beam diffraction image forobserving the crystal orientation of each of the antiferromagnetic layer4 and the pinned magnetic layer 3 from a direction other than theabove-described direction, the crystal orientations of theantiferromagnetic layer 4 and the pinned magnetic layer 3 can besupposed to be as follows. The same equivalent crystal planes of theantiferromagnetic layer 4 and the pinned magnetic layer 3 arepreferentially oriented in parallel with the film plane, and at leastsome of the crystal axes present in the crystal planes are oriented indifferent directions in the antiferromagnetic layer 4 and the pinnedmagnetic layer 3.

Namely, an electron beam is incident from the direction perpendicular tothe interface between the antiferromagnetic layer 4 and the pinnedmagnetic layer 3 to simultaneously obtain transmission electron beamdiffraction images of the antiferromagnetic layer 4 and the pinnedmagnetic layer 3 (refer to FIGS. 20 and 21; FIG. 20 is a schematicdrawing of a diffraction image of the antiferromagnetic layer 4, andFIG. 21 is a schematic drawing of a diffraction image of the pinnedmagnetic layer 3).

In the transmission electron beam diffraction images of theantiferromagnetic layer 4 and the pinned magnetic layer 3, thediffraction spots of the same reciprocal lattice planes are observed.The reciprocal lattice plane, i.e., the projection plane of an electronbeam diffraction mage, is parallel to a crystal plane perpendicular tothe incident electron beam, and for example, crystal planes parallel tothe reciprocal lattice planes include the (111) plane, etc. In thepresent invention, the direction perpendicular to the interface ispreferably the direction of the equivalent crystal axes represented bythe <111> direction, or the crystal planes parallel to the interfacebetween the antiferromagnetic layer and the ferromagnetic layer arepreferably equivalent crystal planes represented by the {111} plane.

Next, the diffraction spots are indexed with reference to the documentof transmission electron beam diffraction images of single crystalstructures. Since the antiferromagnetic layer 4 and the pinned magneticlayer 3 have different lattice constants, i.e., different latticespacings, the transmission electron beam diffraction spots of theantiferromagnetic layer 4 can be easily distinguished from thetransmission electron beam diffraction spots of the pinned magneticlayer 3 by the difference in the distance between each of the spots andthe origin (refer to FIG. 22).

In the present invention, in the diffraction images of theantiferromagnetic layer 4 and the pinned magnetic layer 3, a virtualline (virtual line (1) or (3)) connecting the beam origin and adiffraction spot of the antiferromagnetic layer 4 deviates from avirtual line (virtual line (2) or (4)) connecting the beam origin and adiffraction spot of the pinned magnetic layer 3 with the same indices asthe antiferromagnetic layer 4 (refer to FIG. 22). This means that thesame equivalent crystal orientations present in the crystal planesoriented in parallel with the film plane are in different directions inthe antiferromagnetic layer 4 and the pinned magnetic layer 3.Alternatively, when an indexed diffraction spot is observed only in thediffraction image of one of the antiferromagnetic layer 4 and theferromagnetic layer, the same equivalent crystal orientations of theantiferromagnetic layer 4 and the pinned magnetic layer 3 are indifferent directions.

The transmission electron beam diffraction image of the presentinvention is found to be apparently different from a transmissionelectron beam diffraction image of the comparative example shown inFIGS. 23 to 25 (FIG. 23 is a schematic drawing of a diffraction image ofthe antiferromagnetic layer, FIG. 24 is a schematic drawing of adiffraction image of the pinned magnetic layer, and FIG. 25 is aschematic drawing in which the diffraction images of FIGS. 23 and 24 aresuperposed).

As shown in FIG. 25, a virtual line (5) or (6) connecting a diffractionspot and the beam origin in the diffraction image of theantiferromagnetic layer coincides with the same virtual line in thediffraction image of the ferromagnetic layer.

In the present invention, when the transmission electron beamdiffraction images shown in FIGS. 20 to 22 are obtained, it is supposedthat the same equivalent crystal planes of the antiferromagnetic layer 4and the pinned magnetic layer 3 are preferentially oriented in parallelwith the film plane, and at least some of the same equivalent crystalaxes present are oriented in different directions in the crystal planesof the antiferromagnetic layer 4 and the pinned magnetic layer 3.

Therefore, with the spin valve film exhibiting the above transmissionelectron beam diffraction images, the antiferromagnetic layer 4 isappropriately transformed to the ordered lattice in the heat treatmentstep, thereby obtaining a large exchange coupling magnetic field.

The characteristics of the crystal orientations, the grain boundariesand the twin boundaries of the spin valve thin film element according tothe present invention are described above. However, in order to obtainthe above-described crystal orientations, grain boundaries and twinboundaries, it is necessary to prevent the atoms of theantiferromagnetic layer 4 from being strongly restrained by the crystalstructure of the pined magnetic layer 3 in deposition of theantiferromagnetic layer 4 and the pinned magnetic layer 3. In order toweaken the force of restraint, the interface between theantiferromagnetic layer 4 and the pinned magnetic layer 3 is preferablyin the incoherent state.

The incoherent state means that the atomic arrangements of theantiferromagnetic layer 4 and the pinned magnetic layer 3 do not haveone-to-one correspondence at the interface between both layers. In orderto form such an incoherent state, the difference between the latticeconstants of the antiferromagnetic layer 4 and the pinned magnetic layer3 must be increased.

In addition, the antiferromagnetic layer 4 must be appropriatelytransformed to the ordered lattice by heat treatment. Even when theinterface with the pinned magnetic layer 3 is in the incoherent state,the absence of ordering transformation of the antiferromagnetic layer 4decreases the exchange coupling magnetic field.

The occurrence of the incoherent state in the deposition step, and theoccurrence of ordering transformation greatly depend upon thecomposition ratio of the components and the deposition conditions of theantiferromagnetic layer 4.

In the present invention, the ratio of the element X or elements X+X′ ofthe antiferromagnetic layer 4 is preferably set to 45 to 60 at %. Thisis supposed to bring the interface into the incoherent state during thedeposition step, and cause appropriate ordering transformation of theantiferromagnetic layer 4 during heat treatment.

By using the antiferromagnetic layer 4 having a composition in the aboverange for a spin valve thin film element, it is possible topreferentially orient the same equivalent crystal planes of theantiferromagnetic layer 4 and the pinned magnetic layer 3 in parallelwith the film plane after heat treatment, and orient at least some ofthe same equivalent crystal axes present in the crystal planes indifferent directions in the antiferromagnetic layer 4 and the pinnedmagnetic layer 3. Also, the crystal grain boundaries in theantiferromagnetic layer 4 and the crystal grain boundaries in the pinnedmagnetic layer 3 can be made discontinuous at least a portion of theinterface. Furthermore, the {111} plane of the antiferromagnetic layer 4can be oriented, and the twin boundaries formed in the antiferromagneticlayer 4 can be formed in nonparallel with the interface. Theexperimental results described below indicate that with the compositionin the above range, an exchange coupling magnetic field of 1.58×10⁴(A/m) or more can be obtained.

In the present invention, the ratio of the element X or elements X+X′ ismore preferably set to 49 to 56.5 at %. With this component ratio, anexchange coupling magnetic field of 7.9×10⁴ (A/m) or more can beobtained.

The deposition conditions important for forming the incoherent stateinclude the Ar gas pressure used for depositing the antiferromagneticlayer 4 and the pinned magnetic layer 3, the heat treatment conditions,and the distance between the substrate and the target, substratetemperature, substrate bias voltage, and deposition rate of depositionof the antiferromagnetic layer 4, etc.

In the present invention, the Ar gas pressure is set to, for example, 3mTorr. The heat treatment is performed in a magnetic field at atemperature of 200 to 300° C. under a vacuum of 10⁻⁶ Torr or less for 2hours or more. The distance between the substrate and the target is 80nm.

In the spin valve thin film element having the above-described crystalorientations according to the present invention, at least a portion ofthe interface between the antiferromagnetic layer 4 and the pinnedmagnetic layer 3 can be made incoherent after heat treatment.

The relation between the crystal orientations and the relation betweenthe transmission electron beam diffraction images of theantiferromagnetic layer 4 and the pinned magnetic layer are alsoobserved between the seed layer 22 and the antiferromagnetic layer 4.Namely, the same equivalent crystal planes of the seed layer 22 and theantiferromagnetic layer 4 are preferentially oriented in parallel withthe film plane, and at least some of the same equivalent crystal axespresent in the crystal planes are oriented in different directions inthe seed layer 22 and the antiferromagnetic layer 4.

In a section parallel to the thickness direction, the crystal grainboundaries in the seed layer 22 and the crystal grain boundaries in theantiferromagnetic layer 4 are at least partially discontinuous.

In the seed layer 22 and the antiferromagnetic layer 4 having suchcrystal orientations and crystal grain boundaries, the incoherent stateis easily maintained in at least a portion of the interface between theseed layer 22 and the antiferromagnetic layer 4, thereby causingappropriate ordering transformation of the antiferromagnetic layer 4without being restrained by the crystal structure of the seed layer 2.Therefore, a larger exchange coupling magnetic field can be obtained.

In the present invention, the thickness of the antiferromagnetic layer 4is preferably in the range of 7 nm to 30 nm. In this way, even when thethickness of the antiferromagnetic layer 4 is decreased, an appropriateexchange coupling magnetic field can be produced.

FIG. 2 is a partial sectional view showing the structure of a spin valvethin film element according to another embodiment of the presentinvention.

In this spin valve thin film element, an underlying layer 6, a freemagnetic layer 1 comprising a NiFe alloy film 9 and a Co film 10, anonmagnetic intermediate layer 2, a pinned magnetic layer 3 comprising aCo film 11, a Ru film 12 and a Co film 13, an antiferromagnetic layer 4and a protecting layer 7 are laminated in turn from the bottom to form alaminated film. Furthermore, hard bias layers 5 and conductive layers 8are formed on both sides of the laminated film.

The material of each of the layers is the same as the spin valve thinfilm element shown in FIG. 1.

In the spin valve thin film element shown in FIG. 2, the same equivalentcrystal planes of the antiferromagnetic layer 4 and the pinned magneticlayer 3 are preferentially oriented in parallel with the film plane, andat least some of the same equivalent crystal axes present in the crystalplanes are oriented in different directions in the antiferromagneticlayer 4 and the pinned magnetic layer 3.

In a section of each of the antiferromagnetic layer 4 and the pinnedmagnetic layer 3 taken along the direction (the Z direction shown in thedrawing) parallel to the thickness direction, the crystal grainboundaries in the antiferromagnetic layer 4 and the crystal grainboundaries in the pinned magnetic layer 3 are discontinuous in at leasta portion of the interface.

Therefore, at least a portion of the interface holds the incoherentstate, and the antiferromagnetic layer 4 is appropriately transformed tothe ordered lattice by heat treatment, thereby producing a largeexchange coupling magnetic field.

In the antiferromagnetic layer 4 and the pinned magnetic layer 3, theequivalent crystal planes represented by the {111} plane are preferablypreferentially oriented in parallel with the film plane. In addition, inthe crystal planes, the equivalent crystal orientations represented by<110> orientation are preferably in different directions in theantiferromagnetic layer 4 and the pinned magnetic layer 3.

Where the antiferromagnetic layer 4 is formed on the pinned magneticlayer 3, as in this embodiment, the {111} plane of the antiferromagneticlayer 4 is oriented with difficulty, as compared with the case in whichthe seed layer, the antiferromagnetic layer 4 and the pinned magneticlayer 3 are laminated in this order. However, the {111} plane of theantiferromagnetic layer 4 can be oriented by controlling the depositionconditions. In this case, a twin crystal is formed in at least a portionof the antiferromagnetic layer 4 so that the twin boundaries of the twincrystal are partially nonparallel to the interface. As a result, therate of change in resistance can be improved, and the antiferromagneticlayer 4 is appropriately transformed from the disordered lattice to theordered lattice to obtain a large exchange coupling magnetic field. Theinner angle between each of the twin boundaries and the interface ispreferably 68° to 76°.

In a transmission electron beam diffraction image of each of theantiferromagnetic layer 4 and the pinned magnetic layer 3 of the spinvalve thin film element shown in FIG. 2, obtained by applying anelectron beam in the direction parallel to the interface, a diffractionspot corresponding to a reciprocal lattice point which indicates eachcrystal plane is observed in each of the layers. In these images, afirst virtual line connecting the beam origin and a diffraction spotindicating a crystal plane and positioned in the thickness direction asviewed from the beam origin in the diffraction image of theantiferromagnetic layer 4 coincides with a first virtual line connectingthe beam origin and a diffraction spot having the same indices in thediffraction image of the pinned magnetic layer 3.

Furthermore, in the diffraction images, a second virtual line connectingthe beam origin and a diffraction spot indicating a crystal plane andpositioned in a direction other than the thickness direction as viewedfrom the beam origin in the diffraction image of the antiferromagneticlayer 4 deviates from a second virtual line connecting the beam originand a diffraction spot having the same indices as the antiferromagneticlayer 4 in the diffraction image of the pinned magnetic layer 3.Alternatively, a diffraction spot indicating a crystal plane andpositioned in a direction other than the thickness direction as viewedfrom the beam origin is observed only in the diffraction image of one ofthe antiferromagnetic layer 4 and the ferromagnetic layer.

In this case, the diffraction spots positioned in the thicknessdirection preferably indicate the equivalent crystal planes representedby the {111} plane.

In a transmission electron beam diffraction image of each of theantiferromagnetic layer 4 and the pinned magnetic layer 3 of the spinvalve thin film element shown in FIG. 2, obtained by applying anelectron beam from the direction perpendicular to the interface, adiffraction spot corresponding to a reciprocal lattice point whichindicates each crystal plane is observed in each of the layers. In theseimages, a virtual line connecting the beam origin and a diffraction spotin the diffraction image of the antiferromagnetic layer 4 deviates froma virtual line connecting the beam origin and a diffraction spot havingthe same indices as the antiferromagnetic layer 4 in the diffractionimage of the pinned magnetic layer 3. Alternatively, a diffraction spothaving indices among the diffraction spots is observed only in thediffraction image of one of the antiferromagnetic layer 4 and theferromagnetic layer.

In this case, the direction perpendicular to the interface is preferablythe direction of the equivalent crystal orientations represented by<111> direction, or the crystal planes parallel to the interface betweenthe antiferromagnetic layer and the ferromagnetic layer are preferablythe equivalent crystal planes represented by the {111} plane.

In the present invention, when the above-described transmission electronbeam diffraction images are obtained, it is supposed that the sameequivalent crystal planes of the antiferromagnetic layer 4 and thepinned magnetic layer 3 are preferentially oriented in parallel with thefilm plane, and at least some of the same equivalent crystal axespresent in the crystal planes are oriented in different directions inthe antiferromagnetic layer 4 and the pinned magnetic layer 3.

With the spin valve film exhibiting the above transmission electron beamdiffraction images, the antiferromagnetic layer 4 is appropriatelytransformed to the ordered lattice by heat treatment, thereby obtaininga larger exchange coupling magnetic field than a conventional film.

In the spin valve thin film element shown in FIG. 2, the compositionratio of the element X or elements X+X′ which constitute theantiferromagnetic layer 4 is preferably set to 45 to 60 at %. With thiscomponent ratio, an exchange coupling magnetic field of 1.58×10⁴ (A/m)or more can be obtained.

In the present invention, the composition ratio of the element X orelements X+X′ is more preferably set to 49 to 57 at %. With thiscomponent ratio, an exchange coupling magnetic field of 7.9×10⁴ (A/m) ormore can be obtained.

FIG. 3 is a partial sectional view showing the structure of a spin valvethin film element according to a further embodiment of the presentinvention.

Referring to FIG. 3, an underlying layer 6, a seed layer 22, anantiferromagnetic layer 4, a pinned magnetic layer 3, a nonmagneticintermediate layer 2 and a free magnetic layer 1 are laminated in turnfrom the bottom.

The underlying layer 6 is preferably made of at least one element of Ta,Hf, Nb, Zr, Ti, Mo, and W.

The seed layer 22 preferably has a crystal structure comprising aface-centered cubic crystal in which an equivalent crystal planerepresented by the {111} plane is preferentially oriented in parallelwith the interface with the antiferromagnetic layer 4. The material ofthe seed layer 22 is the same as the spin valve thin film element shownin FIG. 1.

By forming the seed layer 22 below the antiferromagnetic layer 4, thesame equivalent crystal plane as the seed layer 22 is preferentiallyoriented in parallel with the film plane in the antiferromagnetic layer4, the pinned magnetic layer 3, the nonmagnetic intermediate layer 2 andthe free magnetic layer 1 formed on the seed layer 22.

Although the pinned magnetic layer 3 shown in FIG. 3 comprises athree-layer film comprising Co films 11 and 13, and a Ru film 12, othermaterials may be used, and for example, a single layer film may beformed in place of the three-layer film.

Although the free magnetic layer 1 comprises a two-layer film comprisinga NiFe alloy film 9 and a Co film 10, other materials may be used, andfor example, a single layer film may be formed in place of the two-layerfilm.

In the spin valve thin film element shown in FIG. 3, the same equivalentcrystal planes of the antiferromagnetic layer 4 and the pinned magneticlayer 3 are preferentially oriented in parallel with the film plane, andat least some of the same equivalent crystal axes present in the crystalplanes are oriented in different directions in the antiferromagneticlayer 4 and the pinned magnetic layer 3.

In a section of each of the antiferromagnetic layer 4 and the pinnedmagnetic layer 3 taken along the direction (the Z direction shown in thedrawing) parallel to the thickness direction, the crystal grainboundaries in the antiferromagnetic layer 4 and the crystal grainboundaries in the pinned magnetic layer 3 are discontinuous in at leasta portion of the interface.

Therefore, at least a portion of the interface holds the incoherentstate, and the antiferromagnetic layer 4 is appropriately transformed tothe ordered lattice by heat treatment, thereby producing a largeexchange coupling magnetic field.

In the antiferromagnetic layer 4 and the pinned magnetic layer 3, theequivalent crystal planes represented by the {111} plane are preferablypreferentially oriented in parallel with the film plane. In addition, inthe crystal planes, the equivalent crystal orientations represented by<110> orientation are preferably in different directions in theantiferromagnetic layer 4 and the pinned magnetic layer 3.

In the present invention, the equivalent crystal planes represented bythe {111} plane of the antiferromagnetic layer 4 and the pinned magneticlayer 3 are preferably preferentially oriented in parallel with the filmplane, and a twin crystal is formed in at least a portion of theantiferromagnetic layer 4 so that the twin boundaries of the twincrystal are nonparallel to the interface. Therefore, the rate of changein resistance can be increased, and the antiferromagnetic layer 4 can beappropriately transformed from the disordered lattice to the orderedlattice, thereby producing a large exchange coupling magnetic field. Theinner angle between each of the twin boundaries and the interface ispreferably 68° to 76°.

In a transmission electron beam diffraction image of each of theantiferromagnetic layer 4 and the pinned magnetic layer 3 of the spinvalve thin film element shown in FIG. 3, obtained by applying anelectron beam in the direction parallel to the interface, a diffractionspot corresponding to a reciprocal lattice point which indicates eachcrystal plane is observed in each of the layers. In these images, afirst virtual line connecting the beam origin and a diffraction spotindicating a crystal plane and positioned in the thickness direction asviewed from the beam origin in the diffraction image of theantiferromagnetic layer 4 coincides with a first virtual line connectingthe beam origin and a diffraction spot having the same indices as theantiferromagnetic layer 4 in the diffraction image of the pinnedmagnetic layer 3.

Furthermore, in the diffraction images, a second virtual line connectingthe beam origin and a diffraction spot indicating a crystal plane andpositioned in a direction other than the thickness direction as viewedfrom the beam origin in the diffraction image of the antiferromagneticlayer 4 deviates from a second virtual line connecting the beam originand a diffraction spot having the same indices as the diffraction imageof the antiferromagnetic layer 4 in the diffraction image of the pinnedmagnetic layer 3. Alternatively, a diffraction spot indicating a crystalplane and positioned in a direction other than the thickness directionas viewed from the beam origin is observed only in the diffraction imageof one of the antiferromagnetic layer 4 and the ferromagnetic layer.

In this case, the diffraction spots positioned in the thicknessdirection preferably indicate the equivalent crystal planes representedby the {111} plane.

In a transmission electron beam diffraction image of each of theantiferromagnetic layer 4 and the pinned magnetic layer 3 of the spinvalve thin film element shown in FIG. 3, obtained by applying anelectron beam from the direction perpendicular to the interface, adiffraction spot corresponding to a reciprocal lattice point whichindicates each crystal plane is observed in each of the layers. In theseimages, a virtual line connecting the beam origin and a diffraction spotin the diffraction image of the antiferromagnetic layer 4 deviates froma virtual line connecting the beam origin and a diffraction spot havingthe same indices as the antiferromagnetic layer 4 in the diffractionimage of the pinned magnetic layer 3. Alternatively, a diffraction spothaving indices among the diffraction spots is observed only in thediffraction image of one of the antiferromagnetic layer 4 and theferromagnetic layer.

In this case, the direction perpendicular to the interface is preferablythe direction of the crystal orientations represented by <111>orientation, or the crystal planes parallel to the interface between theantiferromagnetic layer and the ferromagnetic layer are preferablyequivalent crystal planes represented by the {111} plane.

In the present invention, when the above-described transmission electronbeam diffraction images are obtained, it is supposed that the sameequivalent crystal planes of the antiferromagnetic layer 4 and thepinned magnetic layer 3 are preferentially oriented in parallel with thefilm plane, and at least some of the same equivalent crystal axespresent in the crystal planes are oriented in different directions inthe antiferromagnetic layer 4 and the pinned magnetic layer 3. With thespin valve film exhibiting the above transmission electron beamdiffraction images, the antiferromagnetic layer 4 is appropriatelytransformed to the ordered lattice by heat treatment, thereby obtaininga larger exchange coupling magnetic field than a conventional film.

In the spin valve thin film element shown in FIG. 3, the compositionratio of the element X or elements X+X′ which constitute theantiferromagnetic layer 4 is preferably set to 45 to 60 at %. With thiscomponent ratio, an exchange coupling magnetic field of 1.58×10⁴ (A/m)or more can be obtained.

In the present invention, the composition ratio of the element X orelements X+X′ is more preferably set to 49 to 56.5 at %. With thiscomponent ratio, an exchange coupling magnetic field of 7.9×10⁴ (A/m) ormore can be obtained.

Referring to FIG. 3, exchange bias layers (antiferromagnetic layers) 16are further formed on the free magnetic layer 1 with a spacecorresponding to a track width Tw in the track width direction (the Xdirection shown in the drawing).

Each of the exchange bias layers 16 is made of a X—Mn alloy (wherein Xis at least one element of Pt, Pd, Ir, Rh, Ru, and Os), and preferably aPtMn alloy or X—Mn—X′ alloy (wherein X′ is at least one element of Ne,Ar, Kr, Xe, Be, B, C, N, Mg, Al, Si, P, Ti, V, Cr, Fe, Co, Ni, Cu, Zn,Ga, Ge, Zr, Nb, Mo, Ag, Cd, Ir, Sn, Hf, Ta, W, Re, Au, Pb, and the rareearth elements).

In the present invention, in the exchange bias layers 16 and the freemagnetic layer 1, the same equivalent crystal planes are preferentiallyoriented in parallel with the film plane, and at least some of the sameequivalent crystal axes present in the crystal planes are oriented indifferent directions in the exchange bias layers 16 and the freemagnetic layer 1.

In a section of each of the exchange bias layers 16 and the freemagnetic layer 1 taken along the direction (the Z direction shown in thedrawing) parallel to the thickness direction, the crystal grainboundaries in the exchange bias layers 16 and the crystal grainboundaries in the free magnetic layer 1 are discontinuous in at least aportion of the interface.

Therefore, at least a portion of the interface holds the incoherentstate, and the exchange bias layers 16 are appropriately transformed tothe ordered lattice by heat treatment, thereby producing a largeexchange coupling magnetic field.

In the exchange bias layers 16 and the free magnetic layer 1, theequivalent crystal planes represented by the {111} plane are preferablypreferentially oriented in parallel with the film plane. In addition, inthe crystal planes, the equivalent crystal orientations represented by<110> orientation are preferably in different directions in the exchangebias layers 16 and the free magnetic layer 1.

In the present invention, the equivalent crystal planes represented bythe {111} plane of the exchange bias layers 16 and the free magneticlayer 1 are preferably preferentially oriented in parallel with the filmplane, and a twin crystal is formed in at least a portion of theexchange bias layers 16 so that the twin boundaries of the twin crystalare nonparallel to the interface. Therefore, the exchange bias layers 16can be appropriately transformed from the disordered lattice to theordered lattice, thereby producing a large exchange coupling magneticfield. The inner angle between each of the twin boundaries and theinterface is preferably 68° to 76°.

In a transmission electron beam diffraction image of each of theexchange bias layers 16 and the free magnetic layer 1 of the spin valvethin film element shown in FIG. 3, obtained by applying an electron beamin the direction parallel to the interface, a diffraction spotcorresponding to a reciprocal lattice point which indicates each crystalplane is observed in each of the layers. In these images, a firstvirtual line connecting the beam origin and a diffraction spotindicating a crystal plane and positioned in the thickness direction asviewed from the beam origin in the diffraction image of the exchangebias layers 16 coincides with a first virtual line connecting the beamorigin and a diffraction spot having the same indices as the exchangebias layers 16 in the diffraction image of the free magnetic layer 1.

Furthermore, in the diffraction images, a second virtual line connectingthe beam origin and a diffraction spot indicating a crystal plane andpositioned in a direction other than the thickness direction as viewedfrom the beam origin in the diffraction image of the exchange biaslayers 16 deviates from a second virtual line connecting the beam originand a diffraction spot having the same indices as the diffraction imageof the exchange bias layers 16 in the diffraction image of the freemagnetic layer 1. Alternatively, a diffraction spot indicating a crystalplane and positioned in a direction other than the thickness directionas viewed from the beam origin is observed only in the diffraction imageof one of the exchange bias layers 16 and the ferromagnetic layer.

In this case, the diffraction spots positioned in the thicknessdirection preferably indicate the equivalent crystal planes representedby the {111} plane.

In a transmission electron beam diffraction image of each of theexchange bias layers 16 and the free magnetic layer 1 of the spin valvethin film element shown in FIG. 3, obtained by applying an electron beamfrom the direction perpendicular to the interface, a diffraction spotcorresponding to a reciprocal lattice point which indicates each crystalplane is observed in each of the layers. In these images, a virtual lineconnecting the beam origin and a diffraction spot in the diffractionimage of the exchange bias layers 16 deviates from a virtual lineconnecting the beam origin and a diffraction spot having the sameindices as the exchange bias layers 16 in the diffraction image of thefree magnetic layer 1. Alternatively, a diffraction spot having indicesamong the diffraction spots is observed only in the diffraction image ofone of the antiferromagnetic layer and the ferromagnetic layer.

In this case, the direction perpendicular to the interface is preferablythe direction of the equivalent crystal orientations represented by<111> direction, or the crystal planes parallel to the interface betweenthe antiferromagnetic layer and the ferromagnetic layer are preferablythe equivalent crystal planes represented by the {111} plane.

In the spin valve thin film element having the above-describedtransmission electron beam diffraction images, it is supposed that thesame equivalent crystal planes of the exchange bias layers 16 and thefree magnetic layer 1 are preferentially oriented in parallel with thefilm plane, and at least some of the same equivalent crystal axespresent in the crystal planes are oriented in different directions inthe exchange bias layers 16 and the free magnetic layer 1. With the spinvalve film exhibiting the above transmission electron beam diffractionimages, the exchange bias layers 16 are appropriately transformed to theordered lattice by heat treatment, thereby obtaining a larger exchangecoupling magnetic field than a conventional film.

The free magnetic layer 1 is put into a single domain state in the Xdirection shown in the drawing by exchange coupling magnetic fieldsbetween the free magnetic layer 1 and the exchange bias layers 16 atboth sides of the free magnetic layer 1. Therefore, magnetization of thetrack width Tw region of the free magnetic layer 1 is oriented in the Xdirection shown in the drawing to an extent depending upon an externalmagnetic field.

In the thus-formed single spin valve magnetoresistive element,magnetization of the track width Tw region of the free magnetic layer 1is changed from the X direction to the Y direction by the externalmagnetic field in the Y direction. The electric resistance changes basedon the change in the magnetization direction of the free magnetic layer1 and the relation to the pinned magnetization direction (the Ydirection) of the pinned magnetic layer 3 so that a leakage magneticfield from a recording medium is detected by a voltage change based onthe change in the electric resistance.

FIG. 4 is a partial sectional view showing the structure of a spin valvethin film element according to a still further embodiment of the presentinvention.

In the spin valve thin film element shown in FIG. 4, a pair of seedlayers 22 is formed with a space corresponding to the track width Tw inthe track width direction (the X direction shown in the drawing), andexchange bias layers 16 are respectively formed on the seed layers 22.

The space between a pair of the seed layers 22 and the exchange biaslayers 16 is filled with an insulating layer 17 made of an insulatingmaterial such as SiO₂, Al₂O₃ or the like.

A free magnetic layer 1 is formed on the exchange bias layers 16 and theinsulating layer 17.

Each of the exchange bias layers 16 is preferably made of a X—Mn alloyor X—Mn—X′ alloy wherein the composition ratio of the element X or X+X′is preferably 45 to 60 at %, and more preferably 49 to 56.5 at %.

The exchange bias layers 16 are appropriately transformed to the orderedlattice by heat treatment without being restrained by the crystalstructure of the free magnetic layer 1, thereby producing a largerexchange coupling magnetic field than a conventional element.

In the present invention, in the exchange bias layers 16 and the freemagnetic layer 1 after heat treatment, the same equivalent crystalplanes are preferentially oriented in parallel with the film plane, andat least some of the same equivalent crystal axes present in the crystalplanes are oriented in different directions in the exchange bias layers16 and the free magnetic layer 1.

In a section of each of the exchange bias layers 16 and the freemagnetic layer 1 taken along the direction (the Z direction shown in thedrawing) parallel to the thickness direction, the crystal grainboundaries in the exchange bias layers 16 and the crystal grainboundaries in the free magnetic layer 1 are discontinuous in at least aportion of the interface.

Therefore, at least a portion of the interface holds the incoherentstate, and the exchange bias layers 16 are appropriately transformed tothe ordered lattice by heat treatment, thereby producing a largeexchange coupling magnetic field.

In the exchange bias layers 16 and the free magnetic layer 1, theequivalent crystal planes represented by the {111} plane are preferablypreferentially oriented in parallel with the film plane. In addition, inthe crystal planes, the equivalent crystal orientations represented by<110> orientation are preferably in different directions in the exchangebias layers 16 and the free magnetic layer 1.

In the present invention, the equivalent crystal planes represented bythe {111} plane of the exchange bias layers 16 and the free magneticlayer 1 are preferably preferentially oriented in parallel with the filmplane, and a twin crystal is formed in at least a portion of theexchange bias layers 16 so that the twin boundaries of the twin crystalare nonparallel to the interface. Therefore, the exchange bias layers 16can be appropriately transformed from the disordered lattice to theordered lattice, thereby producing a large exchange coupling magneticfield. The inner angle between each of the twin boundaries and theinterface is preferably 68° to 76°.

In a transmission electron beam diffraction image of each of theexchange bias layers 16 and the free magnetic layer 1 of the spin valvethin film element shown in FIG. 4, obtained by applying an electron beamin the direction parallel to the interface, a diffraction spotcorresponding to a reciprocal lattice point which indicates each crystalplane is observed in each of the layers. In these images, a firstvirtual line connecting the beam origin and a diffraction spotindicating a crystal plane and positioned in the thickness direction asviewed from the beam origin in the diffraction image of the exchangebias layers 16 coincides with a first virtual line connecting the beamorigin and a diffraction spot having the same indices as the exchangebias layers 16 in the diffraction image of the free magnetic layer 1.

Furthermore, in the diffraction images, a second virtual line connectingthe beam origin and a diffraction spot indicating a crystal plane andpositioned in a direction other than the thickness direction as viewedfrom the beam origin in the diffraction image of the exchange biaslayers 16 deviates from a second virtual line connecting the beam originand a diffraction spot having the same indices as the exchange biaslayers 16 in the diffraction image of the free magnetic layer 1.Alternatively, a diffraction spot indicating a crystal plane andpositioned in a direction other than the thickness direction as viewedfrom the beam origin is observed only in the diffraction image of one ofthe exchange bias layers 16 and the ferromagnetic layer.

In this case, the diffraction spots positioned in the thicknessdirection preferably indicate the equivalent crystal planes representedby the {111} plane.

In a transmission electron beam diffraction image of each of theexchange bias layers 16 and the free magnetic layer 1 of the spin valvethin film element shown in FIG. 4, obtained by applying an electron beamfrom the direction perpendicular to the interface, a diffraction spotcorresponding to a reciprocal lattice point which indicates each crystalplane is observed in each of the layers. In these images, a virtual lineconnecting the beam origin and a diffraction spot in the diffractionimage of the exchange bias layers 16 deviates from a virtual lineconnecting the beam origin and a diffraction spot having the sameindices as the exchange bias layers 16 in the diffraction image of thefree magnetic layer 1. Alternatively, a diffraction spot having indicesamong the diffraction spots is observed only in the diffraction image ofone of the antiferromagnetic layer and the ferromagnetic layer.

In this case, the direction perpendicular to the interface is preferablythe direction of the equivalent crystal orientations represented by the<111> direction, or the crystal planes parallel to the interface betweenthe antiferromagnetic layer and the ferromagnetic layer are preferablythe equivalent crystal planes represented by the {111} plane.

When the above-described transmission electron beam diffraction imagesare obtained, it is supposed that the same equivalent crystal planes ofthe exchange bias layers 16 and the free magnetic layer 1 arepreferentially oriented in parallel with the film plane, and at leastsome of the same equivalent crystal axes present in the crystal planesare oriented in different directions in the exchange bias layers 16 andthe free magnetic layer 1. With the spin valve film exhibiting the abovetransmission electron beam diffraction images, the exchange bias layers16 are appropriately transformed to the ordered lattice by heattreatment, thereby obtaining a larger exchange coupling magnetic fieldthan a conventional element.

The free magnetic layer 1 is put into a single domain state in the Xdirection shown in the drawing by exchange coupling magnetic fieldsbetween the free magnetic layer 1 and the exchange bias layers 16 atboth sides of the free magnetic layer 1. Therefore, magnetization of thetrack width Tw region of the free magnetic layer 1 is oriented in the Xdirection shown in the drawing to an extent depending upon an externalmagnetic field.

Referring to FIG. 4, a nonmagnetic intermediate layer 2 is formed on thefree magnetic layer 1, and a pinned magnetic layer 3 is further formedon the nonmagnetic intermediate layer 2. Furthermore, anantiferromagnetic layer 4 is formed on the pinned magnetic layer 3.

In the present invention, after heat treatment, the same equivalentcrystal planes of the antiferromagnetic layer 4 and the pinned magneticlayer 3 are preferentially oriented in parallel with the film plane, andat least some of the same equivalent crystal axes present in the crystalplanes are oriented in different directions in the antiferromagneticlayer 4 and the pinned magnetic layer 3.

In a section of each of the antiferromagnetic layer 4 and the pinnedmagnetic layer 3 taken along the direction (the Z direction shown in thedrawing) parallel to the thickness direction, the crystal grainboundaries in the antiferromagnetic layer 4 and the crystal grainboundaries in the pinned magnetic layer 3 are discontinuous in at leasta portion of the interface.

Therefore, at least a portion of the interface holds the incoherentstate, and the antiferromagnetic layer 4 is appropriately transformed tothe ordered lattice by heat treatment, thereby producing a largeexchange coupling magnetic field.

In the antiferromagnetic layer 4 and the pinned magnetic layer 3, theequivalent crystal planes represented by the {111} plane are preferablypreferentially oriented in parallel with the film plane. In addition, inthe crystal planes, the equivalent crystal orientations represented by<110> orientation are preferably in different directions in theantiferromagnetic layer 4 and the pinned magnetic layer 3.

In the present invention, the equivalent crystal plane represented bythe {111} plane of the antiferromagnetic layer 4 is preferablypreferentially oriented in parallel with the film plane, and a twincrystal is formed in at least a portion of the antiferromagnetic layer 4so that the twin boundaries of the twin crystal are nonparallel to theinterface. Therefore, the rate of change in resistance can be increased,and the antiferromagnetic layer 4 can be appropriately transformed fromthe disordered lattice to the ordered lattice, thereby producing a largeexchange coupling magnetic field. The inner angle between each of thetwin boundaries and the interface is preferably 68° to 76°.

In a transmission electron beam diffraction image of each of theantiferromagnetic layer 4 and the pinned magnetic layer 3 of the spinvalve thin film element shown in FIG. 4, obtained by applying anelectron beam in the direction parallel to the interface, a diffractionspot corresponding to a reciprocal lattice point which indicates eachcrystal plane is observed in each of the layers. In these images, afirst virtual line connecting the beam origin and a diffraction spotindicating a crystal plane and positioned in the thickness direction asviewed from the beam origin in the diffraction image of theantiferromagnetic layer 4 coincides with a first virtual line connectingthe beam origin and a diffraction spot having the same indices as theantiferromagnetic layer 4 in the diffraction image of the pinnedmagnetic layer 3.

Furthermore, in the diffraction images, a second virtual line connectingthe beam origin and a diffraction spot indicating a crystal plane andpositioned in a direction other than the thickness direction as viewedfrom the beam origin in the diffraction image of the antiferromagneticlayer 4 deviates from a second virtual line connecting the beam originand a diffraction spot having the same indices as the antiferromagneticlayer 4 in the diffraction image of the pinned magnetic layer 3.Alternatively, a diffraction spot indicating a crystal plane andpositioned in a direction other than the thickness direction as viewedfrom the beam origin is observed only in the diffraction image of one ofthe antiferromagnetic layer and the ferromagnetic layer.

In this case, the diffraction spots positioned in the thicknessdirection preferably indicate the equivalent crystal planes representedby the {111} plane.

In a transmission electron beam diffraction image of each of theantiferromagnetic layer 4 and the pinned magnetic layer 3 of the spinvalve thin film element shown in FIG. 4, obtained by applying anelectron beam from the direction perpendicular to the interface, adiffraction spot corresponding to a reciprocal lattice point whichindicates each crystal plane is observed in each of the layers. In theseimages, a virtual line connecting the beam origin and a diffraction spotin the diffraction image of the antiferromagnetic layer 4 deviates froma virtual line connecting the beam origin and a diffraction spot havingthe same indices as the antiferromagnetic layer 4 in the diffractionimage of the pinned magnetic layer 3. Alternatively, a diffraction spothaving indices among the diffraction spots is observed only in thediffraction image of one of the antiferromagnetic layer and theferromagnetic layer.

In this case, the direction perpendicular to the interface is preferablythe direction of the equivalent crystal orientations represented by the<111> direction, or the crystal planes parallel to the interface betweenthe antiferromagnetic layer and the ferromagnetic layer are preferablythe equivalent crystal planes represented by the {111} plane.

When the above-described transmission electron beam diffraction imagesare obtained, it is supposed that the same equivalent crystal planes ofthe antiferromagnetic layer 4 and the pinned magnetic layer 3 arepreferentially oriented in parallel with the film plane, and at leastsome of the same equivalent crystal axes present in the crystal planesare oriented in different directions in the antiferromagnetic layer 4and the pinned magnetic layer 3. With the spin valve film exhibiting theabove transmission electron beam diffraction images, theantiferromagnetic layer 4 is appropriately transformed to the orderedlattice by heat treatment, thereby obtaining a larger exchange couplingmagnetic field than a conventional element.

FIG. 5 is a partial sectional view showing the structure of a dual spinvalve thin film element according to the present invention.

Referring to FIG. 5, an underlying layer 6, a seed layer 22, anantiferromagnetic layer 4, a pinned magnetic layer 3, a nonmagneticintermediate layer 2, and a free magnetic layer 1 are continuouslylaminated. The free magnetic layer 1 comprises a tree-layer filmcomprising, for example, Co films 10 and a NiFe alloy film 9.Furthermore, a nonmagnetic intermediate layer 2, a pinned magnetic layer3, an antiferromagnetic layer 4 and a protecting layer 7 arecontinuously laminated on the free magnetic layer 1.

Furthermore, hard bias layers 5 and conductive layers 8 are formed onboth sides of the laminated film ranging from the underlying layer 6 tothe protecting layer 7.

In this embodiment, the seed layer 22 is formed below theantiferromagnetic layer 4 located below the free magnetic layer 1 shownin the drawing. The composition ratio of the element X or elements X+X′which constitute the antiferromagnetic layer 4 is preferably 45 to 60 at%, and more preferably 49 to 56.5 at %.

In the present invention, after heat treatment, the same equivalentcrystal planes of the antiferromagnetic layer 4 and the pinned magneticlayer 3 are preferentially oriented in parallel with the film plane, andat least some of the same equivalent crystal axes present in the crystalplanes are oriented in different directions in the antiferromagneticlayer 4 and the pinned magnetic layer 3.

In a section of each of the antiferromagnetic layer 4 and the pinnedmagnetic layer 3 taken along the direction (the Z direction shown in thedrawing) parallel to the thickness direction, the crystal grainboundaries in the antiferromagnetic layer 4 and the crystal grainboundaries in the pinned magnetic layer 3 are discontinuous in at leasta portion of the interface.

Therefore, at least a portion of the interface holds the incoherentstate, and the antiferromagnetic layer 4 is appropriately transformed tothe ordered lattice by heat treatment, thereby producing a largeexchange coupling magnetic field.

In the antiferromagnetic layer 4 and the pinned magnetic layer 3, theequivalent crystal planes represented by the {111} plane are preferablypreferentially oriented in parallel with the film plane. In addition, inthe crystal planes, the equivalent crystal orientations represented by<110> orientation are preferably in different directions in theantiferromagnetic layer 4 and the pinned magnetic layer 3.

In the antiferromagnetic layer 4, the equivalent crystal planerepresented by the {111} plane is preferentially oriented in parallelwith the film plane, and a twin crystal is formed in at least a portionof the antiferromagnetic layer 4 so that the twin boundaries of the twincrystal are partially nonparallel to the interface. As a result, therate of change in resistance can be improved, and the antiferromagneticlayer 4 is appropriately transformed from the disordered lattice to theordered lattice to obtain a large exchange coupling magnetic field. Theinner angle between each of the twin boundaries and the interface ispreferably 68° to 76°.

In the dual spin valve thin film element shown in FIG. 5, not only thepined magnetic layer 3 and the antiferromagnetic layer 4 formed belowthe free magnetic layer 1, but also the entire laminated film have thesame crystal orientations as described above.

Namely, in the antiferromagnetic layer 4 and the pinned magnetic layer 3formed above the free magnetic layer 1, the same equivalent crystalplanes are preferentially oriented in parallel with the film plane, andat least some of the same equivalent crystal axes present in the crystalplanes are oriented in different directions in the antiferromagneticlayer 4 and the pinned magnetic layer 3.

In a section of each of the antiferromagnetic layer 4 and the pinnedmagnetic layer 3 taken along the direction (the Z direction shown in thedrawing) parallel to the thickness direction, the crystal grainboundaries in the antiferromagnetic layer 4 and the crystal grainboundaries in the pinned magnetic layer 3 are discontinuous in at leasta portion of the interface.

Therefore, at least a portion of the interface holds the incoherentstate, and the antiferromagnetic layer 4 is appropriately transformed tothe ordered lattice by heat treatment, thereby producing a largeexchange coupling magnetic field.

In the antiferromagnetic layer 4 and the pinned magnetic layer 3, theequivalent crystal planes represented by the {111} plane are preferablypreferentially oriented in parallel with the film plane. In addition, inthe crystal planes, the equivalent crystal orientations represented by<110> orientation are preferably in different directions in theantiferromagnetic layer 4 and the pinned magnetic layer 3.

In the antiferromagnetic layer 4, the equivalent crystal planerepresented by the {111} plane is preferentially oriented in parallelwith the film plane, and a twin crystal is formed in at least a portionof the antiferromagnetic layer 4 so that the twin boundaries of the twincrystal are partially nonparallel to the interface. As a result, therate of change in resistance can be improved, and the antiferromagneticlayer 4 is appropriately transformed from the disordered lattice to theordered lattice to obtain a large exchange coupling magnetic field. Theinner angle between each of the twin boundaries and the interface ispreferably 68° to 76°.

In a transmission electron beam diffraction image of each of theantiferromagnetic layer 4 and the pinned magnetic layer 3 of the spinvalve thin film element shown in FIG. 5, obtained by applying anelectron beam in the direction parallel to the interface, a diffractionspot corresponding to a reciprocal lattice point which indicates eachcrystal plane is observed in each of the layers. In these images, afirst virtual line connecting the beam origin and a diffraction spotindicating a crystal plane and positioned in the thickness direction asviewed from the beam origin in the diffraction image of theantiferromagnetic layer 4 coincides with a first virtual line connectingthe beam origin and a diffraction spot having the same indices as theantiferromagnetic layer 4 in the diffraction image of the pinnedmagnetic layer 3.

Furthermore, in the diffraction images, a second virtual line connectingthe beam origin and a diffraction spot indicating a crystal plane andpositioned in a direction other than the thickness direction as viewedfrom the beam origin in the diffraction image of the antiferromagneticlayer 4 deviates from a second virtual line connecting the beam originand a diffraction spot having the same indices as the antiferromagneticlayer 4 in the diffraction image of the pinned magnetic layer 3.Alternatively, a diffraction spot indicating a crystal plane andpositioned in a direction other than the thickness direction as viewedfrom the beam origin is observed only in the diffraction image of one ofthe antiferromagnetic layer 4 and the ferromagnetic layer.

In this case, the diffraction spots positioned in the thicknessdirection preferably indicate the equivalent crystal planes representedby the {111} plane.

In a transmission electron beam diffraction image of each of theantiferromagnetic layer 4 and the pinned magnetic layer 3 of the spinvalve thin film element shown in FIG. 5, obtained by applying anelectron beam from the direction perpendicular to the interface, adiffraction spot corresponding to a reciprocal lattice point whichindicates each crystal plane is observed in each of the layers. In theseimages, a virtual line connecting the beam origin and a diffraction spotin the diffraction image of the antiferromagnetic layer 4 deviates froma virtual line connecting the beam origin and a diffraction spot havingthe same indices ass the antiferromagnetic layer 4 in the diffractionimage of the pinned magnetic layer 3. Alternatively, a diffraction spothaving indices among the diffraction spots is observed only in thediffraction image of one of the antiferromagnetic layer 4 and theferromagnetic layer.

In this case, the direction perpendicular to the interface is preferablythe direction of the equivalent crystal orientations represented by the<111> direction, or the crystal planes parallel to the interface betweenthe antiferromagnetic layer and the ferromagnetic layer are preferablythe equivalent crystal planes represented by the {111} plane.

In the present invention, when the above-described transmission electronbeam diffraction images are obtained, it is supposed that the sameequivalent crystal planes of the antiferromagnetic layer 4 and thepinned magnetic layer 3 are preferentially oriented in parallel with thefilm plane, and at least some of the same equivalent crystal axespresent in the crystal planes are oriented in different directions inthe antiferromagnetic layer 4 and the pinned magnetic layer 3. With thespin valve film exhibiting the above transmission electron beamdiffraction images, the antiferromagnetic layer 4 is appropriatelytransformed to the ordered lattice by heat treatment, thereby obtaininga larger exchange coupling magnetic field than a conventional element.

FIGS. 6 and 7 are sectional views each showing the structure of an AMRmagnetoresistive element according to the present invention.

Referring to FIG. 6, a soft magnetic layer (SAL layer) 18, a nonmagneticlayer (SHUNT layer) 19, and a magnetoresistive layer (MR layer) 20 arecontinuously laminated in turn from the bottom.

For example, the soft magnetic layer 18 comprises a Fe—Ni—Nb alloy, thenonmagnetic layer 19 comprises a Ta film, and the magnetoresistive layer20 comprises a NiFe alloy.

Furthermore, exchange bias layers (antiferromagnetic layers) 21 areformed on the magnetoresistive layer 20 with a space corresponding tothe track width Tw in the track width direction (the X direction).Although conductive layers are not shown, the conductive layers areformed, for example, on the exchange bias layers 21.

Referring to FIG. 7, a pair of seed layers 22 are formed with a spacecorresponding to the track width Tw in the track width direction (the Xdirection shown in the drawing). Exchange bias layers 21 are formed onthe seed layers 22, and the space between the seed layers 22 and theexchange bias layers 21 is filled with an insulating layer 26 made of aninsulating material such as SiO₂, Al₂O₃, or the like.

Furthermore, a magnetoresistive layer (MR layer) 20, a nonmagnetic layer(SHUNT layer) 19 and a soft magnetic layer (SAL layer) are laminated onthe exchange bias layers 21 and the insulating layer 26.

In the exchange bias layers 21 and the magnetoresistive layer 20 shownin each of FIGS. 6 and 7, the same equivalent crystal planes arepreferentially oriented in parallel with the film plane, and at leastsome of the same equivalent crystal axes present in the crystal planesare oriented in different directions in the exchange bias layers and themagnetoresistive layer 20.

In a section of each of the exchange bias layers 21 and themagnetoresistive layer 20 taken along the direction (the Z directionshown in the drawing) parallel to the thickness direction, the crystalgrain boundaries in the exchange bias layers 21 and the crystal grainboundaries in the magnetoresistive layer 20 are discontinuous in atleast a portion of the interface.

Therefore, at least a portion of the interface holds the incoherentstate, and the exchange bias layers 21 are appropriately transformed tothe ordered lattice by heat treatment, thereby producing a largeexchange coupling magnetic field.

In the exchange bias layers 21 and the magnetoresistive layer 20, theequivalent crystal planes represented by the {111} plane are preferablypreferentially oriented in parallel with the film plane. In addition, inthe crystal planes, the equivalent crystal orientations represented by<110> orientation are preferably in different directions in the exchangebias layers 21 and the magnetoresistive layer 20.

In the present invention, the equivalent crystal planes represented bythe {111} plane of the exchange bias layers 21 are preferablypreferentially oriented in parallel with the film plane, and a twincrystal is formed in at least a portion of the exchange bias layers 21so that the twin boundaries of the twin crystal are nonparallel to theinterface. Therefore, the exchange bias layers 21 can be appropriatelytransformed from the disordered lattice to the ordered lattice, therebyproducing a high exchange coupling magnetic field. The inner anglebetween each of the twin boundaries and the interface is preferably 68°to 76°.

In a transmission electron beam diffraction image of each of theexchange bias layers 21 and the magnetoresistive layer 20 of the AMRthin film element shown in each of FIGS. 6 and 7, obtained by applyingan electron beam in the direction parallel to the interface, adiffraction spot corresponding to a reciprocal lattice point whichindicates each crystal plane is observed in each of the layers. In theseimages, a first virtual line connecting the beam origin and adiffraction spot indicating a crystal plane and positioned in thethickness direction as viewed from the beam origin in the diffractionimage of the exchange bias layers 21 coincides with a first virtual lineconnecting the beam origin and a diffraction spot having the sameindices as the exchange bias layers 21 in the diffraction image of themagnetoresistive layer 20.

Furthermore, in the diffraction images, a second virtual line connectingthe beam origin and a diffraction spot indicating a crystal plane andpositioned in a direction other than the thickness direction as viewedfrom the beam origin in the diffraction image of the exchange biaslayers 21 deviates from a second virtual line connecting the beam originand a diffraction spot having the same indices as the exchange biaslayers 21 in the diffraction image of the magnetoresistive layer 20.Alternatively, a diffraction spot indicating a crystal plane andpositioned in a direction other than the thickness direction as viewedfrom the beam origin is observed only in the diffraction image of one ofthe antiferromagnetic layer and the ferromagnetic layer.

In this case, the diffraction spots positioned in the thicknessdirection preferably indicate the equivalent crystal planes representedby the {111} plane.

In a transmission electron beam diffraction image of each of theexchange bias layers 21 and the magnetoresistive layer 20 of the AMRthin film element shown in each of FIGS. 6 and 7, obtained by applyingan electron beam from the direction perpendicular to the interface, adiffraction spot corresponding to a reciprocal lattice point whichindicates each crystal plane is observed in each of the layers. In theseimages, a virtual line connecting the beam origin and a diffraction spotin the diffraction image of the exchange bias layers 21 deviates from avirtual line connecting the beam origin and a diffraction spot havingthe same indices as the exchange bias layers 21 in the diffraction imageof the magnetoresistive layer 20. Alternatively, a diffraction spothaving indices among the diffraction spots is observed only in thediffraction image of one of the antiferromagnetic layer and theferromagnetic layer.

In this case, the direction perpendicular to the interface is preferablythe direction of the equivalent crystal orientations represented by the<111> direction, or the crystal planes parallel to the interface betweenthe antiferromagnetic layer and the ferromagnetic layer are preferablyequivalent crystal planes represented by the {111} plane.

When the above-described transmission electron beam diffraction imagesare obtained, it is supposed that the same equivalent crystal planes ofthe exchange bias layers 21 and the magnetoresistive layer 20 arepreferentially oriented in parallel with the film plane, and at leastsome of the same equivalent crystal axes present in the crystal planesare oriented in different directions in the exchange bias layers 21 andthe magnetoresistive layer 20. With the spin valve film exhibiting theabove transmission electron beam diffraction images, the exchange biaslayers 21 are appropriately transformed to the ordered lattice by heattreatment, thereby obtaining a larger exchange coupling magnetic fieldthan a conventional element.

In the AMR thin film element shown in each of FIGS. 6 and 7, E regionsof the magnetoresistive layer 20 shown in each of FIGS. 6 and 7 are putinto the single domain state in the X direction by the exchange couplingmagnetic fields produced in the interfaces between the exchange biaslayers 21 and the magnetoresistive layer 20. This induces magnetizationorientation of the D region of the magnetoresistive layer 20 in the Xdirection. Also, a current magnetic field produced by a sensing currentflowing through the magnetoresistive layer 20 is applied to the softmagnetic layer 18 in the Y direction, and a lateral bias magnetic fieldis applied to the D region of the magnetoresistive layer 20 in the Ydirection due to the magnetostatic coupling energy produced by the softmagnetic layer 18. When the lateral bias magnetic field is applied tothe D region of the magnetoresistive layer 20 put into the single domainstate, a change in resistance (magnetoresistive effect property: H—Reffect property) with a change in the magnetic field of the D region ofthe magnetoresistive layer 20 is set to a linear state.

When a recording medium is moved in the Z direction, and a leakagemagnetic field from the recording medium is applied in the Y direction,the resistance value of the D region of the magnetoresistive layer 20changes so that this change is detected as a voltage change.

The method of manufacturing each of the magnetoresistive elements shownin FIGS. 1 to 7 will be described below. Particularly, theantiferromagnetic layer 4 is preferably formed as follows.

As described above, the composition ratio of the element X or elementsX+X′ of the antiferromagnetic layer 4 is preferably 45 to 60 at %, andmore preferably 49 to 56.5 at %. The experimental results describedbelow indicate that with the composition ratio in this range, a largeexchange coupling magnetic field can be obtained.

Therefore, a preferred manufacturing method comprises forming theantiferromagnetic layer 4 having the composition in the above range andthe other layers in the deposition step, and then performing heattreatment.

In the present invention, at least parts of the interfaces between theantiferromagnetic layer 4 and the pinned magnetic layer 3, between theexchange bias layers 16 and the free magnetic layer 1, and between theexchange bias layers 21 and the magnetoresistive layer 20 are preferablyin the incoherent state, and when the seed layer 22 is formed, at leastparts of the interfaces between the seed layer 22 and theantiferromagnetic layer 4 and between the seed layer 22 and the exchangebias layers 16 or 21 are preferably in the incoherent state. Theincoherent state is preferably maintained from the deposition step. Thisis possibly because when the interfaces are in the coherent state in thedeposition step, the antiferromagnetic layer 4, etc. are lesstransformed to the ordered state even by heat treatment.

In order to bring the interface in the incoherent state in thedeposition step, the antiferromagnetic layer 4, etc. are preferablyformed by the following method.

FIG. 8 is a schematic drawing showing the state in which the layers ofthe laminated film shown in FIG. 1 are deposited. As shown in FIG. 8,the seed layer 22 is formed on the underlying layer 6, and then theantiferromagnetic layer 4 comprising a three-layer film is formed. Eachof first, second and third antiferromagnetic layers 23, 24 and 25, whichconstitute the antiferromagnetic layer 4, is made of the X—Mn alloy orX—Mn—X′ alloy.

In the deposition step, the composition ratio of the element X orelements X+X′ which constitute the first and third antiferromagneticlayers 23 and 25 is set to be higher than that of the secondantiferromagnetic layer 24.

The second antiferromagnetic layer 24 formed between the first and thirdantiferromagnetic layers 23 and 25 is made of an antiferromagneticmaterial having a composition close to an ideal composition for easilytransforming the layer from the disordered lattice to the orderedlattice by heat treatment.

The reason for setting the composition ratio of the element X orelements X+X′ of the first and third antiferromagnetic layers 23 and 25to be higher than that of the second antiferromagnetic layer 24 is thatin order to easily transform the antiferromagnetic layer 4 from thedisordered lattice to the ordered lattice by heat treatment, theantiferromagnetic layer 4 must be prevented from being restrained by thecrystal structure of the pinned magnetic layer 3 or the seed layer 22 atthe interface.

The composition ratio of the element X or elements X+X′ of the first andthird antiferromagnetic layers 23 and 25 is preferably 53 to 65 at %,and more preferably 55 to 60 at %. Each of the first and thirdantiferromagnetic layers 23 and 25 preferably has a thickness of 3 Å to30 Å. For example, in the case shown in FIG. 8, the first and thirdantiferromagnetic layers 23 and 25 are formed to a thickness of about 10Å.

The composition ratio of the element X or elements X+X′ of the secondantiferromagnetic layer 24 is 44 to 57 at %, and preferably 46 to 55 at%. With the composition ratio of the element X or elements X+X′ in thisrange, the second antiferromagnetic layer 24 is easily transformed fromthe disordered lattice to the ordered lattice by heat treatment. Thesecond antiferromagnetic layer 24 preferably has a thickness of 70 Å ormore. In the case shown in FIG. 8, the second antiferromagnetic layer 24is formed to a thickness of about 100 Å.

Each of the antiferromagnetic layers 23, 24 and 25 is preferably formedby a sputtering process. In this process, the first and thirdantiferromagnetic layers 23 and 25 are preferably formed under lowersputtering gas pressure than that for the second antiferromagnetic layer24. This can set the composition ratio of the element X or elements X+X′of the first and third antiferromagnetic layers 23 and 25 to be higherthan that of the second antiferromagnetic layer 24.

When the antiferromagnetic layer 4 comprising a single layer film, notthe three-layer film, is formed in the deposition step, the compositionratio of the element X or elements X+X′ can be appropriately changed inthe thickness direction.

When the antiferromagnetic layer 4 is formed by sputtering using anantiferromagnetic material containing the element X and Mn or a targetcomposed of the elements X, X′ and Mn, during deposition of theantiferromagnetic layer 4, the sputtering gas pressure is graduallyincreased as the distance from the seed layer 22 increases. After abouta half of the antiferromagnetic layer 4 is deposited, the sputtering gaspressure is gradually decreased to deposit the remainder of theantiferromagnetic layer 4.

This method gradually decreases the composition ratio (atomic %) of theelement X or elements X+X′ from the interface with the seed layer 22 tothe near center of the antiferromagnetic layer 4 in the thicknessdirection, and gradually increases the composition ratio (atomic %) fromthe near center to the interface with the pinned magnetic layer 3.

It is thus possible to form the antiferromagnetic layer 4 in which thecomposition ratio (atomic %) of the element X or elements X+X′ ishighest near the interfaces with the seed layer 22 and with the pinnedmagnetic layers 3, and lowest near the center of the layer in thethickness direction.

When the composition ratio of total component elements of theantiferromagnetic layer 4 is 100% near the interfaces with the pinnedmagnetic layer 3 and with the seed layer 22, the composition ratio ofthe element X or elements X+X′ is preferably 53 to 65 at %, and morepreferably 55 to 60 at %, near the interfaces.

Also, the composition ratio of the element X or elements X+X′ ispreferably 44 to 57 at %, and more preferably 46 to 55 at %, near thecenter of the antiferromagnetic layer 4 in the thickness directionthereof. The antiferromagnetic layer 4 is preferably formed to athickness of 76 Å or more.

FIG. 9 is a schematic drawing of the spin valve thin film elementshowing the state after heat treatment of the laminated film shown inFIG. 8.

In the present invention, the first and third antiferromagnetic layers23 and 25 each having a high composition ratio of the element X orelements X+X′ are formed in contact with the pinned magnetic layer 3 andthe seed layer 22, respectively, and the second antiferromagnetic layer24 having a composition which is easily appropriately transformed fromthe disordered lattice to the ordered lattice by heat treatment isprovided between the first and third antiferromagnetic layers 23 and 25.Therefore, composition diffusion possibly occurs between the first andthird antiferromagnetic layers and the second antiferromagnetic layer 24at the same time as transformation of the second antiferromagnetic layer24 proceeds by heat treatment. As a result, transformation from thedisordered lattice to the ordered lattice also occurs in the first andthird antiferromagnetic layers 23 and 25 while maintaining theincoherent state at the interfaces with the seed layer 22 and with thepinned magnetic layer 3, thereby causing appropriate transformation overthe entire antiferromagnetic layer 4.

In the spin valve thin film element after heat treatment, the sameequivalent crystal planes of the antiferromagnetic layer 4 and thepinned magnetic layer 3 are preferentially oriented in parallel with thefilm plane, and at least some of the same equivalent crystal axespresent in the crystal planes are oriented in different directions inthe antiferromagnetic layer 4 and the pinned magnetic layer 3.

In a section of each of the antiferromagnetic layer 4 and the pinnedmagnetic layer 3 taken along the direction (the Z direction shown in thedrawing) parallel to the thickness direction, the crystal grainboundaries in the antiferromagnetic layer 4 and the crystal grainboundaries in the pinned magnetic layer 3 are discontinuous in at leasta portion of the interface.

In the present invention, since the seed layer is formed below theantiferromagnetic layer 4, the equivalent crystal plane represented bythe {111} plane of the antiferromagnetic layer 4 is preferentiallyoriented in parallel with the interface, and a twin crystal is formed inat least a portion of the antiferromagnetic layer 4 so that the twinboundaries of the twin crystal are nonparallel to the interface. Theinner angle between each of the twin boundaries and the interface ispreferably 68° to 76°. In the pinned magnetic layer 3, the equivalentcrystal plane represented by the {111} plane is preferablypreferentially oriented.

The antiferromagnetic layer 4 after heat treatment possibly has a regionin which the ratio by atomic % of the element X or elements X+X′ to Mnincreases toward the seed layer 22 and the pinned magnetic layer 3.

In the spin valve thin film element show in FIG. 2, theantiferromagnetic layer 4 may comprise the above-described three films,or a two-layer structure comprising, for example, the firstantiferromagnetic layer 23 in contact with the pinned magnetic layer 3and the second antiferromagnetic layer 24 in contact with the protectinglayer 7. This is because the seed layer 22 shown in FIG. 1 is notprovided in the element shown in FIG. 2.

With the antiferromagnetic layer 4 comprising the two-layer film, theantiferromagnetic layer 4 after heat treatment possibly has a region inwhich the ratio by atomic % of the element X or elements X+X′ to Mnincreases toward the pinned magnetic layer 3.

In the spin valve thin film element shown in FIG. 3, each of theexchange bias layers 16 comprises the same two-layer film as in FIG. 2.The first antiferromagnetic layer 23 is formed in contact with the freemagnetic layer 1, and the second antiferromagnetic layer 24 is formedapart from the free magnetic layer 1.

The antiferromagnetic layer 4 shown in FIG. 3 comprises the samethree-layer film as in FIG. 1. Therefore, the exchange bias layers 16and the antiferromagnetic layer 4 are appropriately transformed to theordered lattice by heat treatment, thereby obtaining a large exchangecoupling magnetic field.

Each of the exchange bias layers 16 after heat treatment possibly has aregion in which the ratio by atomic % of the element X or elements X+X′to Mn increases toward the free magnetic layer 1.

The antiferromagnetic layer 4 after heat treatment possibly has a regionin which the ratio by atomic % of the element X or element X+X′ to Mnincreases toward the pinned magnetic layer 3 and the seed layer 22.

In the method of manufacturing the spin valve thin film element shown inFIG. 4, the antiferromagnetic layer 4 comprises the same two-layer filmas that shown in FIG. 2. The first antiferromagnetic layer 23 is formedin contact with the pinned magnetic layer 3, and the secondantiferromagnetic layer 24 is formed apart from the pinned magneticlayer 3.

Also, each of the exchange bias layers 16 comprises the same three-layerfilm as the antiferromagnetic layer 4 shown in FIG. 1. Therefore, theexchange bias layers 16 and the antiferromagnetic layer 4 areappropriately transformed to the ordered lattice by heat treatment,thereby obtaining a high exchange coupling magnetic field.

Each of the exchange bias layers 16 after heat treatment possibly has aregion in which the ratio by atomic % of the element X or element X+X′to Mn increases toward the free magnetic layer 1 and the seed layer 22.

The antiferromagnetic layer 4 after heat treatment possibly has a regionin which the ratio by atomic % of the element X or element X+X′ to Mnincreases toward the pinned magnetic layer 3.

In the method of manufacturing the dual spin valve thin film elementshown in FIG. 5, as shown in FIG. 10, the antiferromagnetic layer 4located below the free magnetic layer 1 comprises a three-layer filmcomprising a first antiferromagnetic layer 23, a secondantiferromagnetic layer 24 and a third antiferromagnetic layer 25, andthe antiferromagnetic layer 4 located above the free magnetic layer 1comprises a two-layer film comprising a first antiferromagnetic layer 14and a second antiferromagnetic layer 15.

The thicknesses and compositions of the first antiferromagnetic layer23, the second antiferromagnetic layer 24 and the thirdantiferromagnetic layer 25 are the same as described above withreference to FIG. 1.

After the layers are deposited as shown in FIG. 10, heat treatment isperformed. FIG. 11 shows the state after heat treatment. In FIG. 11,composition diffusion possibly occurs in the three-layer film of theantiferromagnetic layer 4 formed below the free magnetic layer 1 toprovide a region in the antiferromagnetic layer 4 after heat treatmentin which the ratio by atomic % of the element X or elements X+X′ to Mnincreases toward the pinned magnetic layer 3 and the seed layer 22.

Also, composition diffusion possibly occurs in the two-layer film of theantiferromagnetic layer 4 formed above the free magnetic layer 1 toprovide a region in the antiferromagnetic layer 4 after heat treatmentin which the ratio by atomic % of the element X or elements X+X′ to Mnincreases toward the pinned magnetic layer 3.

In the method of manufacturing the AMR thin film element shown in FIG.6, each of the exchange bias layers 21 comprises the same two-layer filmas the antiferromagnetic layer 4 formed above the free magnetic layer 1shown in FIG. 10. Each of the exchange bias layers 21 comprises thefirst antiferromagnetic layer 14 formed in contact with themagnetoresistive layer 20, and the second antiferromagnetic layer 15formed apart from the magnetoresistive layer 20.

After heat treatment, the exchange bias layers 21 are appropriatelytransformed to the ordered lattice to produce a large exchange couplingmagnetic field between the exchange bias layers 21 and themagnetoresistive layer 20.

Each of the exchange bias layers 21 after heat treatment possibly has aregion in which the ratio by atomic % of the element X or elements X+X′to Mn increases toward the magnetoresistive layer 20.

In the method of manufacturing the AMR thin film element shown in FIG.7, each of the exchange bias layers 21 comprises the same three-layerfilm as the antiferromagnetic layer 4 shown in FIG. 8. Each of theexchange bias layers 21 comprises the first antiferromagnetic layer 23formed in contact with the magnetoresistive layer 20, the thirdantiferromagnetic layer 25 formed in contact with the seed layer 22, andthe second antiferromagnetic layer 24 formed between the first and thirdantiferromagnetic layers 23 and 25.

After heat treatment, the exchange bias layers 21 are appropriatelytransformed to the ordered lattice to produce a large exchange couplingmagnetic field between the exchange bias layers 21 and themagnetoresistive layer 20.

Each of the exchange bias layers 21 after heat treatment possibly has aregion in which the ratio by atomic % of the element X or element X+X′to Mn increases toward the magnetoresistive layer 20 and the seed layer22.

FIG. 12 is a sectional view of the structure of a reading headcomprising any one of the magnetoresistive elements shown in FIGS. 1 to11, as viewed from the side facing a recording medium.

In FIG. 12, reference numeral 40 denotes a lower shield layer made of,for example, a NiFe alloy, and an upper gap layer 41 is formed on thelower shield layer 40. Furthermore, any one of the magnetoresistiveelements shown in FIGS. 1 to 7 is formed on the lower gap layer 41, anupper gap layer 43 is formed on the magnetoresistive element 42, and anupper shield layer 44 made of a NiFe alloy is formed on the upper gaplayer 43.

Each of the lower gap layer 41 and the upper gap layer 43 is made of aninsulating material, for example, SiO₂, Al₂O₃ (alumina), or the like. Asshown in FIG. 12, the length from the lower gap layer 41 to the uppergap layer 43 corresponds to a gap length G1 which can cope with a higherrecording density as the length G1 decreases.

In the present invention, a large exchange coupling magnetic field canbe produced even when the thickness of the antiferromagnetic layer 4 isdecreased. Therefore, the thickness of a magnetoresistive element can bedecreased, as compared with a conventional element, and thus a thin filmmagnetic head adaptable to an increase in recording density due to gapnarrowing can be manufactured.

Although each of FIGS. 1, 3, 4, 5 and 7 shows the embodiment in whichthe seed layer 22 is formed below the antiferromagnetic layer (or theexchange bias layers 26 or the magnetoresistive layer 20), the presentinvention is not limited to these embodiments.

Although, in a section taken along the direction parallel to thethickness direction, the crystal grain boundaries in theantiferromagnetic layer 4 and the crystal grain boundaries in theferromagnetic layer are discontinuous in at least a portion of theinterface between both layers, different crystal planes of theantiferromagnetic layers and the ferromagnetic layer may bepreferentially oriented in parallel to the film plane. In this case, theantiferromagnetic layer can be appropriately transformed to the orderedlattice by heat treatment, thereby obtaining a high exchange couplingmagnetic field.

EXAMPLES

A spin valve thin having the film structure below was formed, and therelation between the Pt content of a PtMn alloy film constituting anantiferromagnetic layer and the exchange coupling magnetic field (Hex)was examined by changing the Pt content.

The film structure was as follows, from the bottom.

Si substrate/alumina/under layer: Ta (3 nm)/seed layer: NiFe (3nm)/antiferromagnetic layer: Pt_(x)Mn_(100-x) (15 nm)/pinned magneticlayer: Co (1.5 nm)/Ru (0.8 nm)/Co (2.5 nm)/nonmagnetic intermediatelayer: Cu (2.3 nm)/free magnetic layer: Co (1 nm)/NiFe (3 nm)/backedlayer: Cu (1.5 nm)/protecting layer: Ta (3 nm)

The numerical value in parentheses in each of the layers represents thethickness.

The antiferromagnetic layer and the pinned magnetic layer were depositedby a DC magnetron sputtering process. In deposition of theantiferromagnetic layer and the pinned magnetic layer, the Ar gaspressure was 1 to 3 mTorr. In deposition of the antiferromagnetic layer,the distance between the substrate and a target was 70 to 80 mm. Afterthe spin valve film having the above structure was deposited, heattreatment was performed at 200° C. or more for 2 hours or more tomeasure an exchange coupling magnetic field. The experimental resultsare shown in FIG. 13.

FIG. 13 indicates that the exchange coupling magnetic field (Hex)increases as the Pt content X increases from about 50 at % to 55 at %.It is also found that the exchange coupling magnetic field (Hex)gradually decreases as the Pt content X increases from about 55 at %.

In the present invention, a preferred Pt content is considered as acontent with which an exchange coupling magnetic field of 1.58×10⁴ (A/m)can be obtained, and the Pt content is preferably set to 45 to 60 at %based on the experimental results shown in FIG. 13.

A more preferred Pt content is considered as a content with which anexchange coupling magnetic field of 7.9×10⁴ (A/m) can be obtained, andthe Pt content is more preferably set to 49 to 56.5 at % based on theexperimental results shown in FIG. 13.

The possible reason why the exchange coupling magnetic field changeswith the Pt content as described above is that the condition of theinterface between the antiferromagnetic layer and the ferromagneticlayer (pinned magnetic layer) changes with changes in the Pt content.

The lattice constant of the antiferromagnetic layer is found to increaseas the Pt content increases. Therefore, the difference between thelattice constants of the antiferromagnetic layer and the ferromagneticlayer can be increased by increasing the Pt content, thereby easilybringing the interface between the antiferromagnetic layer and theferromagnetic layer into the incoherent state.

On the other hand, by forming the seed layer below the antiferromagneticlayer, as in the above film construction, the {111} plane in each of thelayers formed on the seed layers, such as the antiferromagnetic layer,can easily preferentially be oriented in parallel to the film plane inthe same manner as the seed layer.

It is not always preferred that the Pt content is as high as possible.This is because with an excessively high Pt content, theantiferromagnetic layer cannot be appropriately transformed to theordered lattice by heat treatment.

In the present invention, the seed layer is provided below theantiferromagnetic layer, the Pt content of the composition of theantiferromagnetic layer is controlled to easily cause orderingtransformation and maintain the interface with the ferromagnetic layerin the incoherent state, and the deposition conditions are appropriatelycontrolled. Therefore, the antiferromagnetic layer is appropriatelytransformed to the ordered lattice by heat treatment while maintainingthe incoherent state at the interface with the ferromagnetic layer. Inthe antiferromagnetic layer and the ferromagnetic layer after heattreatment, the same equivalent crystal planes are preferentiallyoriented in parallel to the film plane, and at least some of the sameequivalent crystal axes present in the crystal planes are oriented indifferent directions in the antiferromagnetic layer and theferromagnetic layer.

In observation of a section of each of the antiferromagnetic layer andthe ferromagnetic layer taken along the direction parallel to thethickness direction, the crystal grain boundaries in theantiferromagnetic layer and the crystal grain boundaries in theferromagnetic layer are discontinuous in at least a portion of theinterface between the antiferromagnetic layer and the ferromagneticlayer.

Furthermore, the equivalent crystal planes represented by the {111}plane of the antiferromagnetic layer and the ferromagnetic layer arepreferentially oriented in parallel to the interface, and a twin crystalis formed in at least a portion of the antiferromagnetic layer so thatthe twin boundaries of the twin crystal are nonparallel to theinterface.

As described above, in a section of an exchange coupling film of thepresent invention taken along the direction parallel to the thicknessdirection, the crystal grain boundaries formed in the antiferromagneticlayer, and the crystal grain boundaries formed in the ferromagneticlayer are discontinuous in at least a portion of the interface.

Furthermore, the equivalent crystal plane represented by the {111} planeof the antiferromagnetic layer is preferentially oriented in parallel tothe interface, and a twin crystal is formed in at least a portion of theantiferromagnetic layer so that the twin boundaries of the twin crystalare nonparallel to the interface. In the present invention, the innerangle between each of the twin boundaries and the interface ispreferably 68° to 76°.

When the above film structure is obtained after heat treatment, theantiferromagnetic layer can be appropriately transformed from thedisordered lattice to the ordered lattice to obtain a high exchangecoupling magnetic field.

The above-described exchange coupling film can be applied to variousmagnetoresistive elements, and a magnetoresistive element comprising theexchange coupling film can appropriately cope with higher recordingdensities in future.

1. An exchange coupling film comprising an antiferromagnetic layer and aferromagnetic layer, which are formed in contact with each other so thata magnetization direction of the ferromagnetic layer is pinned in apredetermined direction by an exchange coupling magnetic field producedat an interface between both layers, wherein the antiferromagnetic layeris made of an antiferromagnetic material comprising an element X (atleast one element selected from Pt, Pd, Ir, Rh, Ru, and Os) and Mn; andin a section of the exchange coupling film in parallel with a thicknessdirection thereof, crystal grain boundaries formed in theantiferromagnetic layer and crystal grain boundaries formed in theferromagnetic layer extend in a nonparallel direction with respect to aninterface between the ferromagnetic layer and antiferromagnetic layerand are discontinuous in at least a portion of the interface.
 2. Anexchange coupling film according to claim 1, wherein in theantiferromagnetic layer and the ferromagnetic layer, equivalent crystalplanes represented by a {111} plane are preferentially oriented inparallel with the interface.
 3. An exchange coupling film according toclaim 1, wherein the antiferromagnetic layer is made of a X—Mn—X′ alloy(wherein X′ represents at least one element selected from Ne, Ar, Kr,Xe, Be, B, C, N, Mg, Al, Si, P, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Ga, Ge,Zr, Nb, Mo, Ag, Cd, Ir, Sn, Hf, Ta, W, Re, Au, Pb, and the rare earthelements).
 4. An exchange coupling film according to claim 3, whereinthe X—Mn—X′ alloy is an interstitial solid solution in which the elementX′ enters interstices in space lattices composed of the element X andMn, or a substitution solid solution in which lattice points of crystallattices composed of the element X and Mn are partially substituted bythe element X′.
 5. An exchange coupling film according to claim 1,wherein a composition ratio of the element X or elements (X+X′) is 45 at% to 60 at %.
 6. An exchange coupling film according to claim 1, whereinat least a portion of the interface between the antiferromagnetic layerand the ferromagnetic layer is incoherent.
 7. A magnetoresistive elementcomprising an antiferromagnetic layer, a pinned magnetic layer formed incontact with the antiferromagnetic layer so that a magnetizationdirection of the pinned magnetic layer is pinned by an exchange couplingmagnetic field with the antiferromagnetic layer, a free magnetic layerformed on the pinned magnetic layer with a nonmagnetic intermediatelayer provided therebetween, and a bias layer for orienting amagnetization direction of the free magnetic layer in a directioncrossing the magnetization direction of the pinned magnetic layer,wherein the antiferromagnetic layer and the pinned magnetic layer formedin contact with the antiferromagnetic layer comprise an exchangecoupling film according to claim
 1. 8. A magnetoresistive elementcomprising an antiferromagnetic layer, a pinned magnetic layer formed incontact with the antiferromagnetic layer so that a magnetizationdirection of the pinned magnetic layer is pinned by an exchange couplingmagnetic field with the antiferromagnetic layer, a free magnetic layerformed on the pinned magnetic layer with a nonmagnetic intermediatelayer provided therebetween, and antiferromagnetic exchange bias layersformed on or below the free magnetic layer with a space corresponding toa track width Tw, wherein the exchange bias layers and the free magneticlayer comprise an exchange coupling film according to claim 1, andmagnetization of the free magnetic layer is pinned in a predetermineddirection.
 9. A magnetoresistive element comprising nonmagnetic layerslaminated on and below a free magnetic layer, pinned magnetic layerslocated on one of the nonmagnetic intermediate layers and below theother nonmagnetic intermediate layer, antiferromagnetic layers locatedon one of the pinned magnetic layers and below the other pinned magneticlayer, for pinning a magnetization direction of each of the pinnedmagnetic layers in a predetermined direction by an exchange couplingmagnetic field, and a bias layer for orienting a magnetization directionof the free magnetic layer in a direction crossing the magnetizationdirection of the pinned magnetic layers, wherein the antiferromagneticlayers and the pinned magnetic layers respectively formed in contactwith the antiferromagnetic layers comprise an exchange coupling filmaccording to claim
 1. 10. A magnetoresistive element comprising amagnetoresistive layer and a soft magnetic layer which are laminatedwith a nonmagnetic layer provided therebetween, and antiferromagneticlayers formed on or below the magnetoresistive layer with a spacetherebetween corresponding to a track width Tw, wherein theantiferromagnetic layers and the magnetoresistive layer comprise anexchange coupling film according to claim 1.